Bar code scanner with collimated scan volume

ABSTRACT

An optical scanner comprising an automatic (i.e., triggerless) portable bar code symbol reading device with an omnidirectional scanning engine mounted within the head portion of its housing, and adapted for use with an associated base unit. The bar code symbol reading device produces a confined scanning volume for omnidirectional scanning of code symbols presented therein, while preventing unintentional scanning of code symbols on nearby objects located outside of the confined scanning volume.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to laser scanningsystems, and more particularly to an automatic bar code symbol readingsystem in which an automatic hand-supportable laser scanner can beinterchangeably utilized as either a portable hand-held laser scanner inan automatic “hands-on” mode of operation, or as a stationary laserprojection scanner in an automatic “hands-free” mode of operation.

[0003] 2. Brief Description of the Prior Art

[0004] Bar code symbols have become widely used in many commercialenvironments such as, for example, point-of-sale (POS) stations inretail stores and supermarkets, inventory and document tracking, anddiverse data control applications. To meet the growing demands of thisrecent technological innovation, bar code symbol readers of varioustypes have been developed for scanning and decoding bar code symbolpatterns and producing symbol character data for use as input inautomated data processing systems.

[0005] In general, prior art hand-held bar code symbol readers usinglaser scanning mechanisms can be classified into two major categories.

[0006] The first category of hand-held laser-based bar code symbolreaders includes manually-actuated trigger-operated systems havinglightweight, hand-held laser scanners which can be supported in the handof the user. The user positions the hand-held laser scanner at aspecified distance from the object bearing the bar code symbol, manuallyactivates the scanner to initiate reading and then moves the scannerover other objects bearing bar code symbols to be read. Prior art barcode symbol readers illustrative of this first category are disclosed inU.S. Pat. No. 4,387,297 to Swartz; U.S. Pat. No. 4,575,625 to Knowles;U.S. Pat. No. 4,845,349 to Cherry; U.S. Pat. No. 4,825,057 to Swartz, etal.; U.S. Pat. No. 4,903,848 to Knowles; U.S. Pat. No. 5,107,100 toShepard, et al.; U.S. Pat. No. 5,080,456 to Katz, et al.; and U.S. Pat.No. 5,047,617 to Shepard, et al.

[0007] The second category of hand-held laser-based bar code symbolreaders includes automatically actuated systems having lightweighttriggerless hand-held laser scanners which can be supported in the handof the user. The user positions the hand-held laser scanner, at aspecified distance from the object bearing the bar code the presence ofthe object is automatically detected, the presence of the bar codesymbol on the object is detected, and thereafter the detected bar codesymbol automatically read. Prior art illustrative of this secondcategory of laser-based bar code symbol reading systems are disclosed inU.S. Pat. No. 4,639,606 to Boles, et al., and U.S. Pat. No. 4,933,538 toHeiman, et al.

[0008] While prior art hand-held and stationary laser scanners haveplayed an important role in the development of the bar code symbolindustry, these devices have, however, suffered from a number ofshortcomings and drawbacks. For example, hand-held laser scanners,although portable and lightweight, are not always convenient to use inassembly-line applications where the user processes bar coded objectsover an extended period of time, or where the user requires the use ofboth hands in order to manipulate the objects. In some applications,hand-held laser scanners are difficult to manipulate whilesimultaneously moving objects or performing other tasks at apoint-of-sale terminal. Stationary laser scanners, on the other hand,provide a desired degree of flexibility in many applications by allowingthe user to manipulate bar coded objects with both hands. However, bytheir nature, stationary laser scanners render scanning large, heavyobjects a difficult task as such objects must be manually moved into orthrough the laser scan field.

[0009] Attempting to eliminate the problems associated with the use ofhand-held and stationary laser scanners, U.S. Pat. No. 4,766,297 toMcMillan discloses a bar code symbol scanning system which combines theadvantages of hand-held and stationary fixed laser scanners into asingle scanning system which can be used in either a hands-on orhands-free mode of operation. The bar code symbol scanning system inU.S. Pat. No. 4,766,297 includes a portable hand-held laser scanningdevice for generating, electrical signals descriptive of a scanned barcode symbol. In the hands-on mode of operation, a trigger on thehand-held laser1 scanning device is manually actuated each time a barcode symbol on an object is to be read. The system further includes afixture1 having a head portion for receiving and supporting thehand-held laser scanning device, and a base portion above which the headportion is supported at a predetermined distance. In the hands-free modeof operation, the hand-held laser scanning device is supported by thefixture head portion above the fixture base portion in order to allowobjects bearing bar code symbols to pass between the head and baseportions of the fixture. In order to detect the presence of an objectbetween the head and base portions of the fixture, the fixture alsoincludes an object sensor operably connected to the hand-held laserscanning device. When the object sensor senses an object between thehead portion and the base portion, the object sensor automaticallyinitiates the hand-held laser scanning device supported in the fixtureto read the bar code symbol on the detected object.

[0010] While the bar code symbol scanning system of U.S. Pat. No.4,776,297 permits reading of printed bar code information using either aportable “hands-on” or stationary “hands-free” mode of operation, thissystem suffers from several significant shortcomings and drawbacks aswell.

[0011] In particular, in the hands-on mode of operation, scanning barcode symbols requires manually actuating a trigger each time a bar codesymbol is to be read. In the hands-free mode of operation, scanning barcode symbols requires passing the object bearing the bar code betweenthe head and base portions of the fixture. However, in many instanceswhere both hands are required to manipulate a bar coded object, theobject is too large to be passed between the head and base portions ofthe fixture and thus scanning of the bar code symbol is not possible.

[0012] In an attempt to address such problems, several hand-heldprojection laser scanners have been developed for omnidirectional codesymbol scanning. Examples of such systems include the NCR 7890presentation scanner from the NCR Corporation and the LS9100omnidirectional laser scanner from Symbol Technologies, inc. While eachof these systems produces an omnidirectional laser scan pattern from ahand-supportable housing and have hands-free and hands-on modes ofoperation, each of these scanning devices suffer from a number ofshortcomings and drawbacks. In particular, the spatial extent of thelaser scan pattern produced from each of these scanners frequentlyresults in the inadvertent scanning of code symbols on products placednear the scanner during its hands-free mode of operation. In thehands-on mode of operation, it is virtually impossible to use thescanners to read bar code symbol menus provided in diverse applicationenvironments. Moreover, in each of these scanner designs, the scanner istethered to its base unit by a power/signal cord, and the user isrequired to handle the scanner housing in an awkward manner in thehands-on mode of operation, resulting in strain and fatigue and thus adecrease in productivity. In addition, the control structure provided ineach of these hand-held projection scanners operates the scannercomponents in a manner which involves inefficient consumption ofelectrical power, and prevents diverse modes of automatic code symbolreading which would be desired in portable scanning environments.

[0013] Thus, there is a great need in the bar code symbol reading artfor a bar code symbol reading system which overcomes the above describedshortcomings and drawbacks of prior art devices and techniques, whileproviding greater versatility in its use.

OBJECTS AND SUMMARY OF THE INVENTION

[0014] Accordingly, it is a primary object of the present invention toprovide a fully automatic bar code symbol reading system having anautomatic hand-supportable laser scanning device which can be used at apoint-of-sale (POS) station as either a portable hand-supported laserscanner when operated in its automatic hands-on mode of operation, or asa stationary laser projection scanner when operated in its automatichands-free mode of operation.

[0015] It is another object of the present invention to provide such anautomatic bar code symbol reading system, wherein a highly collimatedlaser scanning pattern is projected from the hand-supportable deviceabout a projection axis, and comprises laser scanning planes whichintersect within a narrowly confined scanning volume extending about theprojection axis so that bar code symbols disposed within the scanningvolume can be read omnidirectionally, while inadvertent scanning of barcode symbols outside of the scanning volume is prevented.

[0016] It is another object of the present invention to provide such anautomatic bar code symbol reading system, wherein the projection axisabout which the narrowly confined scanning volume extends issubstantially coplanar with the longitudinal axis of the head and ifhandle portions of the hand-supportable housing.

[0017] It is another object of the present invention to provide anautomatic hand-supportable laser projection scanner having acenter-of-mass which provides easy handling, consistent withergonometric design principles, for fatigue-free omnidirectionalscanning of bar code symbols.

[0018] Another object of the present invention to provide automatichand-supportable omnidirectional laser protection scanner with ahand-supportable housing that allows to user to easily control thedirection of its projection axis by way of the handle portion of thehousing, and thus align the narrowly confined scanning volume; of thescanner with the bar code symbol on the object to be scanned andidentified.

[0019] Another object of the present invention to provide a portableautomatic hand-supportable omnidirectional laser projection scanner witha power-conserving control system that provides battery power to thesystem components of the scanner in an intelligent manner.

[0020] Another object of the present invention to provide an automatichand-supportable omnidirectional laser projection scanner having ahand-supportable housing with a scan-head that visually, indicates thedirection of the projection axis, for intuitive hand-supportedomnidirectional scanning of bar code symbols within the narrowlyconfined scanning volume extending thereabout.

[0021] It is another object of the present invention to provide such anautomatic bar code symbol reading system, in which one or more bar codesymbols on an object can be automatically read in a consecutive manner.

[0022] A further object is to provide such an automatic bar code symbolreading device, in which the automatic hand-supportable bar code(symbol) reading device has an infrared light object detection fieldwhich spatially encompasses at least a portion of its volumetricscanning field along the operative scanning range of the device, therebyimproving the laser beam pointing efficiency of the device during theautomatic bar code reading process of the present invention.

[0023] Another object of the present invention is to provide such anautomatic bar code reading system with a scanner support stand thatsupports the hand-supportable housing of the device in a selectedmounting position, and permits complete gripping of the handle portionof the hand-supportable housing prior to removing it therefrom.

[0024] Another object of the present invention is to provide anautomatic bar code symbol reading system, in which battery power from asupply within the hand-supportable housing of its portable bar codesymbol reading device is automatically metered out and provided to thepower distribution circuitry thereof for a predetermined time periodwhich is reset upon the occurrence of either the manual actuation of anexternally mounted power reset button, the reading (i.e. scanning anddecoding) of a valid bar code symbol, or the placement of thehand-supportable bar code symbol reading device within its scannersupport stand.

[0025] A further object of the present invention is to provide such anautomatic bar code symbol reading device, with a novel automatic powercontrol circuit that effectively conserves the consumption of batterypower therein, without compromising the operation, or performance of thedevice during its diverse modes of automatic operation.

[0026] It is another object of the present invention is to provide anautomatic hand-supportable bar code reading device having both long andshort-range modes of bar code symbol reading, automatically selectablein a variety of different ways, (e.g. by, placing the hand-supportabledevice within its support stand, removing it therefrom).

[0027] Another object of the present invention is to provide such amulti-mode automatic bar code symbol reading device, so that it can: beused in various bar code symbol reading applications, such as, forexample, charge coupled device (CCD) scanner emulation, counter-topprojection scanning in the hands-free long-range mode of operation, orthe like.

[0028] Another object of the present invention is to provide anautomatic hand-supportable bar code reading device with a programmablyselectable mode of operation that prevents multiple reading of the samebar code symbol due to dwelling of the laser scanning beam upon a barcode symbol for an extended period of time, yet allows a plurality ofbar code symbols (e.g. representing the same UPC) to be read in aconsecutive manner even though they are printed on the same, orapparently the same, object or surface, as often is the case ininventory scanning applications.

[0029] A further object of the present invention is to provide apoint-of-sale station (POS) incorporating the automatic bar code symbolreading system of the present invention.

[0030] It is a further object of the present invention is to provide anautomatic hand-supportable bar code reading device having a controlsystem which has a finite number of states through which the device maypass during its automatic operation, in response to diverse conditionsautomatically detected within the object detection and scanning fieldsof the device.

[0031] Another object of the present invention is to provide a portable,automatic bar code symbol reading device, wherein the laser beamscanning motor is operated at a lower angular velocity during its objectdetection state to conserve battery power consumption and facilitaterapid steady-state response when the device is induced into its bar codesymbol detection and bar code symbol reading states of operation.

[0032] Another object of the present invention is to provide a portableautomatic bar code symbol reading device, wherein the laser beamscanning motor is denergized during its object detection state toconserve battery power consumption therewhile, and is momentarilyoverdriven to facilitate rapid steady-state response when the deviceundergoes a transition from the object detection state to the bar codesymbol detection state of operation.

[0033] Another object of the present invention is to provide a novelmechanism for mounting a projection laser scanning platform within thehead portion of an automatic hand-supportable omnidirectional projectionlaser scanner.

[0034] Another object of the present invention is to provide a novelomnidirectional laser scanning platform for use within an automaticportable projection laser scanner.

[0035] Another object of the present invention is to provide a bar codesymbol reading system having at least one hand-supportable bar codesymbol reading device which, after each successful reading of a codesymbol, automatically synthesizes and then transmits a data packet to abase unit positioned within the data transmission range of the bar codesymbol reading device, and upon the successful receipt of thetransmitted data packet and recovery of symbol character data therefrom,the base unit transmits an acoustical acknowledgement signal that isperceptible to the user of the bar code symbol reading device residingwithin the data transmission range thereof.

[0036] A further object of the present invention is to provide such asystem with one or more automatic (i.e., triggerless) hand-supportablelaser-based bar code symbol reading devices, each of which is capable ofautomatically transmitting data packets to its base unit after eachsuccessful reading of a bar code symbol.

[0037] A further object of the present invention is to provide such abar code symbol reading system in which the hand-supportable bar codesymbol reading device can be used as either a portable hand-supportedlaser scanner in an automatic hands-on mode of operation, or as astationary laser projection scanner in an automatic hands-free mode ofoperation.

[0038] A further object of the present invention is to provide such abar code symbol system in which the base unit contains a batteryrecharging device that automatically recharges batteries contained inthe hand-supportable device when the hand-supportable device issupported within the base unit.

[0039] It is another object of the present invention to provide such anautomatic bar code symbol reading system with a mode of operation thatpermits the user to automatically read one or more bar code symbols onan object in a consecutive manner.

[0040] A further object of the present invention is to provide such anautomatic bar code symbol reading system, in which a plurality ofautomatic hand-supportable bar code symbol reading devices are used inconjunction with a plurality of base units, each of which is assigned toa particular bar code symbol reading device.

[0041] A further object of the present invention is to provide such anautomatic bar code symbol reading system, in which radio frequency (RF)carrier signals of the same frequency are used by each hand-supportablebar code symbol reading device to transmit data packets to respectivebase units.

[0042] A further object of the present invention is to provide such anautomatic bar code symbol reading system, in which a novel data packettransmission and reception scheme is used to minimize the occurrence ofdata packet interference at each base unit during data packet reception.

[0043] A further object of the present invention is to provide such anautomatic bar code symbol reading system, in which the novel data packettransmission and reception scheme enables each base unit to distinguishdata packets associated with consecutively different bar code symbolsread by a particular bar code symbol reading device, without thetransmission of electromagnetic-based data packet acknowledgment signalsafter receiving each data packet at the base unit.

[0044] It is a further object of the present invention to provide anautomatic hand-supportable bar code reading device having a controlsystem which has a finite number of states through which the device maypass during its automatic operation, in response to diverse conditionsautomatically detected within the object detection and scan fields ofthe device.

[0045] It is yet a further object of the present invention to provide aportable, fully automatic bar code symbol reading system which iscompact, simple to use and versatile.

[0046] Yet a further object of the present invention is to provider anovel method of reading bar code symbols using an automatichand-supportable omnidirectional laser scanning device.

[0047] These and further objects of the present invention will becomeapparent hereinafter and in the claims to Invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] For a fuller understanding of the Objects of the Invention, theDetailed Description of the Illustrated Embodiments of the PresentInvention should be read in conjunction with the accompanying drawings,wherein:

[0049]FIG. 1A is an elevated perspective view of the illustrativeembodiment of the automatic bar code symbol reading system hereof, withits hand-supportable bar code symbol reading device shown supportedwithin the scanner support stand portion of its matching base unit, andarranged for automatic hands-free operation;

[0050]FIG. 1B is an elevated perspective view of the illustrativeembodiment of the automatic bar code symbol reading device hereof, shownbeing used in its automatic hands-on mode of operation;

[0051]FIG. 1C is an elevated side view of the illustrative embodiment ofthe automatic bar code symbol reading device hereof, illustrating thatthe mass balance of the hand-supportable bar code symbol reading devicehas been designed to minimize torques about the point of pivot of thehousing which occurs about the user's index finger in order to maximizeits ergonomic handling efficiency eliminate fatigue during automatichands-on, omnidirectional laser scanning operations;

[0052]FIG. 1D is an elevated side view of the illustrative embodiment ofthe automatic bar code symbol reading device hereof, illustrating thespatial alignment of the longitudinal axis of the head portion of thescanner and the projection axis of the laser scanning platform containedtherein;

[0053]FIG. 1E is an elevated side view of the illustrative embodiment ofthe automatic bar code symbol reading device hereof, shown supportedwithin the scanner support stand portion of its matching base unit,arranged for automatic hands-free operation in a first scanningposition;

[0054]FIGS. 1F and 1G provide an elevated side view of the illustrativeembodiment of the automatic bar code symbol reading device hereof, shownsupported within the scanner support stand portion of its matching baseunit, arranged for automatic hands-free operation in a second scanningposition;

[0055]FIG. 2A is an elevated side view of the illustrative embodiment ofthe automatic bar code symbol reading device of the present invention,illustrating the spatial relationship between the object detection andscan fields of the device, and the long and short-ranges of programmedobject detection, bar code presence detection, and bar code symbolreading;

[0056]FIG. 2B is a plan view of the automatic bar code symbol readingdevice taken along line 2A-2A of FIG. 2;

[0057]FIG. 3A is an elevated, cross-sectional side view of the automaticbar code symbol reading device of the present invention, taken along itslongitudinal axis, showing the various components contained therein;

[0058]FIG. 3B is an elevated, end view of the automatic bar code symbolreading device of the present invention, taken along line 3B-3B of FIG.1D, showing the various components contained therein;

[0059]FIG. 4 is an elevated side view of the laser scanning platform ofthe present invention realized on its shock-mounted optical bench,removed from the housing of the hand-supportable bar code symbol readingdevice of the present invention;

[0060]FIG. 5A is a plan view of the optical bench of the laser scanningplatform of FIG. 4, shown with the stationary array of mirrors, rotatingpolygonal mirror and motor removed therefrom for illustrative purposes;

[0061]FIG. 5B is a view of the laser scanning platform of the presentinvention taken along line 5B-5B of FIG. 4;

[0062]FIG. 5C is an elevated side view of the optical bench of FIG. 5A,shown with the stationary mirror support bracket removed therefrom forillustrative purposes;

[0063]FIG. 5D is schematic diagram illustrating the physical layout ofcomponents on the analog signal processing board supported on theoptical bench of the laser scanning platform of FIG. 4;

[0064] FIGS. 6A1, 6A2 and 6B provide a geometrical optics model of thestationary mirror array of the laser scanning platform of theillustrative embodiment, graphically defining the various angles used toconfigure the stationary mirrors relative to the central reference planethereof;

[0065]FIG. 6C is a geometrical optics model of the stationary mirrorarray of the laser scanning platform of the illustrative embodiment,graphically defining the various physical dimensions stationary mirrorsrelative to the central reference plane thereof;

[0066]FIG. 6D is a geometrical optics model of the stationary mirrorarray of the laser scanning platform of the illustrative embodiment,graphically defining the various physical dimensions stationary mirrorsrelative to the central reference plane thereof;

[0067]FIGS. 7A and 7B are cross-sectional views of the 3-D laserscanning volume of the illustrative embodiment, taken parallel to thelight transmissive window at about 1.0″ and 5.0″ therefrom;

[0068]FIG. 8 is a system block functional diagram of the automatic barcode symbol reading system of the present invention, illustrating theprincipal components integrated with the control (sub)-system thereof;

[0069]FIG. 8A is a schematic diagram of the automatic power supply unitaboard the automatic bar code symbol reading device of the presentinvention;

[0070]FIG. 8B is a functional logic diagram of the oscillator circuit inthe Application Specific Integrated Circuit (ASIC) chip in the automaticbar code symbol reading device of the present invention;

[0071]FIG. 8C is a timing diagram for the oscillator circuit of FIG. 8B;

[0072]FIG. 8D is a block functional diagram of the object detectioncircuit (i.e., system activation means) in the ASIC chip in theautomatic bar code symbol reading device of the present invention;

[0073]FIG. 8E is a functional logic diagram of the first control circuit(C.sub.1) of the control system of the present invention;

[0074]FIG. 8F is a functional logic diagram of the clock divide circuitin the first control circuit C.sub.1 of FIG. 8E;

[0075]FIG. 8G is table setting forth Boolean logic expressions for theenabling signals produced by the first control circuit C.sub.1;

[0076]FIG. 8H is a functional block diagram of the analog to digital(A/D) signal conversion circuit in the ASIC chip in the bar code symbolreading device of the present invention;

[0077]FIG. 8I is a functional logic diagram of the bar code symbol(presence) detection circuit in the ASIC chip in the bar code symbolreading device of the present invention;

[0078]FIG. 8J is a functional logic diagram of the clock divide circuitin the bar code symbol detection circuit of FIG. 8I;

[0079]FIG. 8K is a schematic representation of the time window andsubintervals maintained by the bar code symbol detection circuit duringthe bar code symbol detection process,

[0080]FIG. 8L is a functional logic diagram of the second controlcircuit (C.sub.2) in the ASIC chip in the automatic bar code symbolreading device of the present invention;

[0081]FIG. 8M is Boolean logic table defining the functionalrelationships among the input and output signals into and out from thesecond control circuit C.sub.2 of FIG. 8N;

[0082]FIG. 8N is a schematic representation of the format of each datapacket transmitted from the data packet transmission circuit of FIG. 9.

[0083]FIG. 9 is a functional block diagram of the data packettransmission circuit of the bar code symbol reading device of thepresent invention;

[0084]FIG. 10 is a schematic representation illustrating several groupsof data packets transmitted from the bar code symbol reading devicehereof in accordance with the principles of data packet transmission andreception scheme of the present invention;

[0085]FIG. 11 is a schematic representation of an exemplary set offgroups of data packet pseudo-randomly transmitted from neighboring barcode symbol reading devices, and received at one base unit in physicalproximity therewith;

[0086]FIG. 12 is a schematic representation of an exemplary set of datapackets simultaneously transmitted from three neighboring bar codesymbol reading devices of the present invention, and received at theassociated base units assigned thereto;

[0087] FIGS. 13A, 13AA, 13B, 13C, taken together, show a high level flowchart of the control process performed by the control subsystem of thebar code symbol reading device, illustrating various modes of objectdetection, bar code presence detection and bar code symbol reading;

[0088]FIG. 14 is a state transition diagram illustrating the variousstates that the automatic hand-supportable bar code symbol readingdevice of the illustrative embodiment may undergo during the course ofits programmed operation;

[0089]FIG. 15A is a perspective view of the scanner support standportion of the countertop base unit of the present invention;

[0090]FIG. 15B is a perspective view of the base plate portion of thecountertop base unit of the present invention;

[0091]FIG. 16 is a functional block diagram of the data packet receivingand processing circuitry and the acknowledgment signal generatingcircuitry of the present invention realized on the printed circuit boardin the base unit shown in FIGS. 15A to 15C;

[0092]FIG. 16A is a functional block diagram of the radio receiversubcircuit of the data packet receiving circuit of FIG. 16;

[0093]FIG. 16B is a functional block diagram of the digitally controlledacoustical acknowledgment signal generating circuit of the presentinvention;

[0094]FIGS. 17 and 17A is a flow chart illustrating the steps undertakenduring the control process carried out in the base unit of FIG. 15A;

[0095]FIG. 18A is perspective view of a point-of-sale (POS) stationaccording to the present invention, showing the automatichand-supportable bar code symbol reading device hereof being used in itsautomatic “hands-free” long-range mode of operation; and

[0096]FIG. 18B is a perspective view of the POS station of FIG. 18A,showing the symbol reading device hereof being used in its automatic“hands-on” short-range mode of operation.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT OF THE PRESENTINVENTION

[0097] As shown in FIGS. 1 to 3B, automatic bar code symbol readingsystem 1 of the illustrative embodiment of the present inventioncomprises an automatic (i.e., triggerless) portable bar code (symbol)reading device 2 operably associated with a base unit 3 having a scannersupport stand 4 pivotally connected thereto, for releasably supportingthe automatic bar code symbol reading device 2 at any one of a number ofpositions above of a counter surface at a Point of Sale (POS) station.In the preferred embodiment, the bar code symbol reading device 2 isoperably connected with its the base unit 3 by way of a one wayelectromagnetic link 5 that is momentarily created between bar codesymbol reading device 2 and its mated base unit 3 after the successfulreading of each bar code symbol by the bar code symbol reading device.Operable interconnection between the base unit and a host system (e.g.,electronic cash register system, data collection device, etc.) 6 isachieved by a flexible multiwire communications cable. 7 extending fromthe base unit and plugged directly into the data-input communicationsport of the host computer system 6. In the illustrative embodiment,electrical power from a low voltage direct current (DC) power supply(not shown) is provided to the base unit by way of a flexible powercable 8. Notably, this DC power supply can be realized in host computersystem 6 or as a separate DC power supply adapter pluggable into aconventional 3-prong electrical socket. In other embodiments of thepresent invention, cables 7 and 8 can be integrated to provide a singleflexible, multi-wire cable for transmission of power to the base unitand data to the host system. As will be described in greater detailhereinafter, a rechargeable battery power supply unit 20 is containedprimarily within the handle portion of the bar code symbol readingdevice 2 in order to energize the electrical and electro-opticalcomponents within the device.

[0098] As illustrated in FIGS. 1A through 1B, scanner support stand 4 isparticularly adapted for receiving and supporting portable bar codesymbol reading device 2 without user support, thus providing astationary, automatic hands-free mode of operation. In general, portablebar code symbol reading device 2 includes an ultra-light weighthand-supportable housing 9 having a head portion 9A and a contouredhandle portion 9B. As will be described in greater detail hereinafter,head portion 9A encloses electro-optical components which are arrangedin a novel scanning platform 10 of ultra compact construction whichrenders possible the production of a highly collimated scanning pattern11 through light transmission window 12 for the purpose of scanning barcode symbols on objects within a narrowly confined scanning (i.e., 3-Dscan field) volume 13, while preventing unintentional scanning of, barcode symbols on objects located outside thereof at point of sale (POS)stations. Thus, by minimizing the amount of counter-space that must beclear (i.e. free) of bar coded items at point of sale POS stations, thelaser scanner of the present invention provides retailers with greatercounter-space availability for displaying merchandise and the like, yetwithout sacrificing the; increase in check-out performance and workerproductivity associated with the use of bar code symbol scanners at POSstations.

[0099] As illustrated in FIGS. 1 through 1C, the base unit 3 includes abase portion 14 which can be realized in a variety of different ways.For example, the base portion 14 can be realized, as a compact stand forsupport upon a countertop surface as shown in FIG. 18, or it can berealized as a support mount for vertical wall-mounting. In eitherembodiment, the function of the scanner stand 4 is to support the devicein any one of a plurality of positions above a workspace 19 which may bea counter surface in POS applications. With this arrangement, the highlycollimated scanning pattern 11 can be projected about the projectionaxis 17 above the counter surface in any one of a plurality oforientations corresponding to the plurality of positions.

[0100] As shown in FIGS. 1A and 15A, base portion 14 contains electroniccircuitry realized on a PC board 16 for carrying out various types offunctions, namely: reception of electrical power from the host systemand coupling electrical power to the rechargeable battery containedwithin the hand-supportable housing; reception of data packetstransmitted from the automatic bar code symbol reading device, andprocessing the same for data recovery; generation of acoustical and/oroptical acknowledgement signals; and transmission of symbol characterdata to the host system. Each of these functions will be described ingreater detail hereinafter with reference to FIGS. 15A and 15B.

[0101] As illustrated in FIGS. 1B and 1C in particular, the head portion9A continuously extends into contoured handle portion 9B at an obtuseangle .alpha. which, in the illustrative embodiment, is about 115degrees. It is understood, however, that in other embodiments obtuseangle a may be in the range of about 100 to about 150 degrees. Asillustrated in FIG. 1C, the mass balance of the device is particularlydesigned so that when the device is held within the user's hand, theindex finger of the user is disposed beneath the head portion of thehousing, and provides a pivot point about which there is substantiallyzero torque acting upon the device, preventing it from rotating ineither direction about the index finger. Instead, the resultant forcedistribution acting upon the user's hand is aligned in the direction ofgravitational forces, as indicted in FIG. 1C. The effect of thismass-balanced scanner design is to minimize the torque imposed on theuser's wrists and forearms while using the bar code symbol readingdevice in the hands-on mode of operation. This, in turn, minimizes theamount of energy which the user must expend during hands-on scanningoperations, thereby reducing wrist and arm fatigue and increasing workerproductivity. In addition to the above, advantages, the hand-supportablehousing hereof is sculptured (i.e., form-fitted) to the human hand sothat automatic hands-on; scanning is rendered easy and effortless. Also,the ergonomic housing design eliminates the risks of musculoskeletaldisorders, such as carpal tunnel syndrome, which can result fromrepeated biomechanical stress commonly associated with pointing priorart gun-shaped scanners at bar code symbols, and squeezing a trigger toactivate the laser scanning beam, and then releasing the trigger.

[0102] As best shown in FIGS. 1G, 15A and 15B, stand portion 4 of thebase unit 3 is pivotally supported with respect to the base portion byway of pivot pins 22A and 22B. In order to releasably hold the standportion of the base unit relative to the base portion thereof in any oneof a number of provided scanning positions, a releasable stand-lockingmechanism 23 is provided. As shown in FIG. 1G, the locking mechanism isrealized as a set of projections 24 formed on the inside surface of thesupport arms 4A of the stand portion of the base unit, and aprojection-catch 25 formed on the adjacent surface of the base portion.These structure features of the base unit are shown in FIG. 1G. rhefunction of the projection catch 25 is to releasably engage one of theprojections 24 associated with the selected scanning position. Gentlerotation of the head portion of the scanner while supported in its standcauses the projection caught in the projection-catch 25 to releasetherefrom, allowing the scanner to be repositioned as desired. At theresulting scanning position, the corresponding projection 24automatically engages with the projection-catch 25 and locks the standportion of the base unit relative to the base portion thereof. Inaddition, to allow the base unit to easily rotate relative to itssupport surface, the bottom of the base portion is realized as aturntable structure that allows its bottom section 26A to be stationaryrelative to the support surface (i.e. countertop) 27, while the uppersection 26B is fixed relative to the balance of the base portion of thebase unit. A pivot 26C is used to pivotally connect the upper and lowersections together for easy rotation of the base unit relative to thesupport surface.

[0103] In FIGS. 1E and 1F, the automatic bar code symbol reading systemof the present invention is arranged in two extreme scanningconfigurations during the automatic hands-free mode of system operation.In these different scanning configurations, the stand portion of thebase unit is arranged differently with respect to the base portion ofthe base unit. In FIG. 1E, the stand portion of the base unit is shownsupporting the hand-supportable projection scanning device hereof sothat its narrowly-confined 3-D scanning volume 13 is projected in adirection slightly off-parallel to the counter surface upon which thebase unit is a supported. In this hands-free scanning configuration,code symbols on large objects can be easily scanned by simply presentingthe code symbol to the narrowly-confined scanning volume 13 projected,along the “pointing direction” (i.e. longitudinal axis) of the headportion of the scanner housing. In FIG. 1F, the stand portion of thebase unit is shown supporting the hand-supportable projection scanningdevice hereof so that its scanning volume is projected downwardly, in adirection passing through the counter surface upon which the base unitis supported. In this hands-free scanning configuration, code symbols onsmall objects can be easily scanned by simply presenting to the codesymbol to the narrowly-confined scanning volume 13 projected beneath thehead portion of the scanner housing.

[0104] As illustrated in FIGS. 2A through 3B, the head portion 9A of thehand-supportable housing has a light transmission aperture 12A formed inthe front portion thereof. As shown, the light transmission window 12 ismounted over the entire light transmission aperture. In the preferredembodiment, the spectral transmission characteristics of the lighttransmission window are such that all wavelengths greater (i.e. longer)than slightly less than 670 nm (e.g. longer than 665 nm) are permittedto exit and enter the interior volume of the housing with minimumattenuation. As a result of such characteristics, the visible laser lineat 670 nanometers and the infra-red (IR) spectral line at 870 nm(produced from the object sensing circuitry hereof) are allowed topropagated through the transmission window, out of the head portion ofthe housing, reflect from an object/bar code surface, and return throughthe transmission window. Notably, all other surfaces of thehandsupportable housing are opaque to electromagnetic radiation in thevisible band.

[0105] As illustrated in FIGS. 2, and 2A, in particular, the bar codesymbol reading device 2 generates from its laser scanning platform 10,two different types of fields external to its hand-supportable housing.As explained below, these fields function to carry out a novel bar codesymbol reading process according to the principles of the presentinvention. The first field, referred to as the “object detection field”,indicated by broken and dotted lines 30, is provided external to thehousing for detecting energy reflected off an object (bearing a bar codesymbol) located in the object detection field. As shown in FIGS. 2A and2B, the second field 31, referred to as the “scan field” or “3-D scanfield” (i.e. narrowly-confined scanning volume 13), has a multiplicityof laser beam scanning planes contained therewithin projected externalto the head portion of the housing. The function of the scanning volume(i.e. 3-D scan field) is to scan a bar code symbol on an objectautomatically detected in the object detection field. In the preferredembodiment, bar code symbol scanning is achieved using a scanned visiblelaser beam which, after reflecting off the bar code symbol in thescanning volume 13, produces laser scan data that is collected for thepurpose of automatically detecting the bar code symbol and subsequentlyreading (i.e., scanning and decoding) the same.

[0106] In general, detected energy reflected from an object duringobject detection can be optical radiation or acoustical energy, eithersensible or non-sensible by the user, and may be either generated fromthe automatic bar code reading device or an external ambient source.However, as will be described in greater detail hereinafter, theprovision of such energy is preferably achieved by transmitting a widebeam of pulsed infrared (IR) light away from transmission aperture 11,in a direction substantially parallel to longitudinal axis 16 of thehand-supportable housing. In the preferred embodiment, the objectdetection field, from which such reflected energy is collected, isdesigned to have a narrowly diverging pencil-like geometry ofthree-dimensional volumetric expanse, which is spatially coincident withat least a portion of the transmitted infrared light beam. This featureof the present invention ensures that an object residing within theobject detection field will be illuminated by the infrared light beam,and that infrared light reflected therefrom will be directed generallytowards the transmission aperture of the housing where it can beautomatically detected to indicate the presence of the object within theobject detection field. In response to object presence detection, avisible laser beam is automatically generated within the interior of thebar code symbol reading device, projected through the light transmissionaperture of the housing and repeatedly scanned across the scanningvolume, within which at least a portion of the detected object lies. Atleast a portion of the scanned laser light beam will be scattered andreflected if the object and directed back towards and through lighttransmissive window 11 for collection and detection within the interiorof the bar code symbol reading device, and subsequently processed in amanner which will be described in detail hereinafter.

[0107] To ensure that the user can quickly align the visible laser beamwith the bar code symbol on the detected object, the object detectionfield of the preferred embodiment is designed to spatially encompass asignificant portion of the 3-D scanning volume along the operativescanning range of the device, as illustrated in FIGS. 2A and 2B, for thefirst illustrative embodiment of the present invention. This structuralfeature of the present invention improves the laser beam pointingefficiency of the device during the automatic bar code symbol readingprocess.

[0108] As best shown in FIGS. 3A and 3B, the laser scanning platform(i.e., laser scanning engine) 10 of the present invention is mountedwithin the head portion of the hand-supportable housing by way of athree-point shock-absorbing mounting mechanism, which will be describedin greater detail hereinbelow. In the illustrative embodiment, thehand-supportable housing is realized as a five-piece split-housingconstruction comprising: a first housing portion 9C carrying threespaced-apart mounting posts 29A, 29B and 29C, and providing a batterystorage bay 30 for storage of a (rechargeable) battery supply unit 32; asecond housing half 9D providing posts 31A and 31B which engage withsupport posts 29A and 29B when the first and second housing halves arebrought together; a battery cover 9E for placement over the batterystorage bay 30; a housing end cap 9F for placement over the ends of thefirst and second housing halves; and a housing bumper 9G for supportingthe light transmission window 12 and holding securely together the frontends of the first and second housing halves when the subcomponents ofthe housing are assembled together. Provided within the battery storagebay, is an electrical socket 33 designed to receive rechargeable battery32 when it is installed within the bay when the bay cover 9E is removed.An electrical wire harness 34 is used to connect the battery socket 33to a printed circuit (PC) board 50 supported upon the laser scanningplatform 10, carrying digital scan data processing and controlcircuitry. Apertures 35A and 35B are formed in the end portion of thehousing handle to allow electrodes 51A and 51B on the battery 32 toestablish electrical contact with charging electrodes 52A and 52Bprovided within the support bay 60 of the stand portion of the base unitwhen the scanning device is operated in its hands-free mode ofoperation. Preferably, the above-described housing subcomponents aremade from a rugged, lightweight plastic material using injection-moldingtechniques well known in the art.

[0109] As will be described in greater detail hereinafter, the datapacket transmission circuit of copending application Ser. No.08/292,237, now U.S. Pat. No. 5,808,285 is realized on PC board 50,along with the microprocessor used to implement symbol decoding, dataformatting and system control functions. Electrical power supplied fromrechargeable battery 32 is provided to the digital signalsprocessing/control board 50 by way of flexible wire harness 34. Asshown, a transmitting antenna 53 is operably connected to the datapacket transmission circuit on the digital signal processing board andis mounted within hand-supportable housing 9 for transmission of a datapacket modulated RF carrier signal. The structure and thefunctionalities of the automatic bar code symbol reading system hereofwill be described in greater detail hereinafter with reference to FIGS.8 to 14.

[0110] In FIG. 4, the laser scanning platform 10 is shown removed fromits housing. As shown, the laser scanning platform comprises an assemblyof subcomponents assembled upon an optical bench 34 with respect to acentral longitudinal reference plane 35 referenced in Fogs. SA through5B, in particular. This subcomponent assembly comprises: a scanningpolygon 36 having four light reflective surfaces 36A,36B, 36C and 36D,each disposed at an tilt angle a with respect to the rotational axis ofthe polygon; an electrical motor 37 mounted on the optical bench, andhaving a rotatable shaft on which polygon 36 is mounted for rotationablemovement therewith; an array of stationary mirrors 38A, 38B, 38C, 38Dand 38E fixedly mounted with respect to the optical bench; a laser beamproduction module 39, fixedly mounted above the rotating polygon, forproducing a laser beam having a circularized beam cross-section, andessentially free of astigmatism along its length of propagation; ananalog signal processing board 40, fixedly mounted over the rotatablepolygon, and carrying a photodetector 41 for detecting reflected laserlight and producing analog scan data signals, and analog signalprocessing control circuits 42 for performing various functions,including analog scan data signal processing; a light collecting mirror43, disposed at a height above the central stationary mirror 38C, forcollecting light rays reflected off the rotating polygon and focusingthe same onto the photodetector on the analog board; and a beamdirecting surface 44, realized as a flat mirror mounted on the lightcollecting mirror 38C, for directing the laser beam from the laser beamproduction module to the rotating polygon disposed therebeneath. Asshown, these subcomponents are mounted relative to the optical bench 34according to the Specifications set forth in FIGS. 6A through 6B.

[0111] In FIGS. 5A through 5D, the subcomponents of the laser scanningplatform are shown in greater detail. In particular, optical bench 34 isshown in FIG. 5A with the scanning motor 37 and, stationary mirrorelements 38A through 38E removed for illustration purposes. As shown,stationary mirror brackets 45 is mounted upon the optical bench 34 andhas five mirror support elements 45A through 45B, disposed beneath thelocations of their respective mirrors 38A, 38B, 38C, 38D and 38E. Asshown in FIG. 5B, the analog signal processing board 40 is disposedabove the scanning polygon 36 and extends at an acute angle with respectto the plane of the optical bench. The analog signal processing board 40is supported in this position and orientation by a pair of supportbracket 46A and 46B. Support brackets 46A and 46B, in turn, aresupported by a pair of support posts 47A and 47B mounted to the middleportion of the optical bench 34, as shown in FIGS. 5A and 5B. Asillustrated in FIG. 4, the position of these support posts are slightlyforward of the rotational axis of the polygon motor.

[0112] As best shown in FIG. 5A, the transverse axis of the lightcollecting mirror 43 is perpendicular to the central reference plane ofthe optical bench. The stationary light reflective surface (i.e. mirror)38C also has a transverse axis extending substantially perpendicularlywith respect to the central reference plane 34. Stationary lightreflective surfaces 38B and 38D are symmetrically disposed on oppositesides of the central reference plane, respectively, and immediatelyadjacent stationary light reflective surface 38C. Stationary lightreflective surfaces (i.e. mirrors) 38A and 38E are symmetricallydisposed on opposite sides of the central reference plane, andimmediately adjacent stationary light reflective surfaces 38B and 38D,respectively, and adjacent rotating polygon 36.

[0113] As best illustrated in FIG. 5C the angle of declination of thelight collecting mirror 43 is selected so that the incident laser beamthereon from the laser beam production module 38 is redirected towardsthe rotating polygon during laser beam scanning operations. The focallength of the light collecting mirror 43 is, selected so that collectedlight rays from the mirror are focused upon the photodetector 41,centrally mounted upon the analog signal processing board 40. In theillustrative embodiment, light focusing mirror 43 is realized fromground-polished glass, or molded plastic, coated with a mirror-finish byvapor deposition.

[0114] As shown in FIG. 5C, the photodetector 41 and light collectingmirror 43 are aligned along a common optical axis which is disposedwithin the central longitudinal plane. As shown in FIG. 5D, thephotodetector 41 is mounted on the analog signal processing board 40along with signal processing circuits and signal connector elements,namely: optical filters 186A; visible laser diode drive circuitry 178;motor drive circuitry 181; IR preamp circuitry 187; IR transmit andreceive circuitry 106; signal processing circuitry IC2; scan signalpreamplification circuitry 187; microprocessor port connector 300; andVLD/motor port connector 301. The function of such components will bedescribed in greater detail hereinafter.

[0115] The laser beam production module 39 of the laser scanningplatform hereof may be realized in a variety of ways. Preferably, eachembodiment thereof comprises a visible laser diode for producing avisible laser beam, and associated optics for circularizing the laserbeam and eliminating astigmatism therefrom along its direction ofpropagation. In the illustrative embodiment, the associated opticscomprises an aspheric collimating lens, a beam circularizing prism, anda holographically formed light diffractive grating configured in such amanner that the above-described functions are realized during laser beamproduction. The manner in which such a laser beam production module canbe constructed without the use of aperture stops is taught in copendingapplication Ser. No. 08/573,949, now abandoned incorporated herein byreference.

[0116] The particular parameters used to configure the opticalcomponents of the laser scanning module are schematically represented inFIGS. 6A1 through 6D. In FIGS. 6A1 and 6A2, a geometrical optics modelis provided for the illustrative, embodiment of the laser beam scanningplatform of the present invention. Within this geometrical optics model,stationary mirror surface 38A through 38E are designated by surfaceparameters S1 through S5, respectively. Each of these mirror surfaces islocated about the central longitudinal plane 35 of the system, whichfunctions as a reference plane. In the illustrative embodiment, thedistance between the rotational axis of the polygon and the base of thecentral mirror surfaces S3 is 34 millimeters in the, illustrativeembodiment, whereas the base-to-base distance between mirror surfaces S1and S5 is about 35 millimeters.

[0117] As shown in the geometrical optics model, the angled ofinclination of the four mirrored surfaces on the polygon 36A, 36B, 36C,36D are set forth in the Table of FIG. 6B. The angle of elevation f(i.e. bend) of each of the stationary mirrors 38A, 38B, 38C, 38D and 38Eare listed in Table of FIG. 6A1. As shown in FIG. 6B, the angle ofinclination of the stationary mirrors is references with respect to theplane of the optical bench. As shown in FIG. 6A1, the angle of twist afor each stationary mirror is referenced relative to the centrallongitudinal plane 35. The twist angle for the stationary mirrors areset forth in the Table of FIG. 6A1. Notably, as central stationarymirror S3 is disposed transversely relative to the central longitudinalplane, the twist angle for this stationary mirror is 90.degree. Thelaterally disposed stationary mirrors S2 and S4 have the same twistangle of 43.75.degree., whereas stationary mirrors S1 and S5 have thesame twist angles of 40.5.degree.

[0118] The heightwise and widthwise dimensions of the stationaryreflective surfaces, in part, determine the length of the scanlineswithin the scan field. These dimensions are indicated in FIG. 6C for theillustrative embodiment. Notably, the perimetrical dimensions of thesestationary mirrors are irregular in order to form a tightly-nestedstationary mirror array arranged about the rotating polygon 36. Theexact surface dimensions are indicated in FIG. 6C. The heightwise andwidthwise dimensions of the mirrors on the rotating polygon areindicated in FIG. GD. When constructed in accordance with theSpecifications disclosed herein, the laser scanning platform of theillustrative embodiment will produce a highly collimated set of scanningplanes which extend from the light transmission window and intersectabout the projection axis 17 to form a highly collimated scanningpattern within a narrowly-confined 3-D scanning volume thereabout.Two-dimensional cross-section characteristics of the resulting laserscanning pattern at about 1.5 and 6 sinches from the transmission windoware shown in FIGS. 7A and 7B.

[0119] When assembled and configured as described above, the laserscanning platform 10 is mounted with the upper and lower halves of thehand-supportable housing 9A and 9B. Mounting is achieved by way ofresiliently securing shock-mounting support posts 29A, 29B and 29C tocorresponding mounting holes formed within the optical bench 35 usingrubber grommets and screws. As shown in FIG. 7, the assembled laserscanning platform (i.e. engine) is installed within the housing in amanner described above. As shown, PC board 5G is mounted to theunderside of the plastic optical bench by way of mechanical fastenersknown in the art. The function of PC board 50 is provide substrate uponwhich the decode/control processor, RF data packet transmissioncircuitry and power. distribution circuitry of the laser scanning devicehereof are realized. In order that the shock-absorbing mounting systemcan operate properly, it is important that sufficient clearance isprovided between the outermost extensions of the scanning platform tandthe interior wall surface of upper portion of the housing. In this way,the scanning platform is permitted to undergo gross displacements in thedirections of the dominant oscillatory modes of system when the deviceis dropped onto the floor, knocked into solid objects and the like undernormal or otherwise expected operating environments.

[0120] Having described the physical construction of the laser scanningengine 10 of the present invention, it is appropriate at this junctureto describe in greater detail the manner in which the laser scanningpattern is produced from the laser scanning platform hereof.

[0121] Upon detection of an object within the object detection field 30,a laser beam is produced from the laser beam production module 39 and isdirected towards beam directing surface 44 mounted on the lightcollecting mirror 43. The laser beam reflects from the beam directingsurface 44 towards the mirrored facets on the rotating scanning polygon36. As the polygon spins, the incident laser beam reflects off therotating mirrors 36A through 36D and sweeps the laser beam about itsrotational axis along a plurality of different paths which intersect thestationary array of mirrors 38A through 38E on the optical bench. Duringeach revolution of the scanning polygon, the laser beam reflects off therotating mirrors and therewhile is repeatedly swept across the array ofstationary mirrors thereby producing first, second, third, fourth andfifth groups of plural scan lines, respectively. These plural groups ofscanlines shown in FIGS. 7A and 7B are projected out through the lighttransmission window and intersect about the projection axis 17 extendingfrom the light transmission window, and within the narrowly confinedscanning volume 13. In the illustrative embodiment, the intersection ofthe laser scanning planes extends from adjacent (e.g. about 9.5″ from)the light transmission window to at least about 10.0 inches therefrom soas to produce a highly collimated projected scanning pattern within thenarrowly confined 3-D scanning volume. Within this 3-D scanning volume,a bar code, symbol can be scanned omnidirectionally, while preventingunintentional scanning of code symbols on objects located outsiderthereof.

[0122] As illustrated in the cross-sectional diagrams of FIGS. 7A and7B, there exists a particular relationship among the scanlines of thelaser scanning pattern of the illustrative embodiment. In particular,each scan line in each group of scan lines is substantially parallel toeach other scan line in that group of scan lines. As a result, when thecode symbol is presented to the highly collimated scanning patternprojected within narrowly confined scanning field, the code symbol isautomatically scanned therewithin independent of the orientation of thecode symbol within the scanning field (i.e. scanning volume). At least aportion of the laser light reflected from the scanned code symbol isdirected through the light transmission window, reflected off thestationary light reflective surfaces, reflected off the rotatingmirrors, collected by the light focusing mirror, and received by thephotodetector 41, whereupon an electrical signal is produced for use indecode signal processing. The details of such signal processingoperations, and the preferred means for achieving the same, can be bestunderstood with a detailed description of the scan and control dataprocessing circuitry embodied with the laser scanning device of thepresent invention.

[0123] As shown in FIG. 8, the automatic bar code symbol reading systemof the present invention comprises the automatic laser scanning deviceof the illustrative embodiment in combination with a number of systemcomponents. These additional system components include: a primaryoscillator circuit 101 for producing a primary clock signal CLK for useby the object detection circuit 107; a first RC timing network 102 forsetting the oscillation frequency, of the primary oscillator circuit;first control means 104, realized as a first control circuit C.sub.1,for performing localized system control functions; a second RC timingnetwork 105 for setting a timer T.sub.1 in control circuit C.sub.1;means (e.g., an object sensing circuit 106 and an object detectioncircuit 107) for producing a first activation control signal A.sub.1=1upon the detection of an object bearing a bar code in at least a portionof the object detection field; a laser beam scanning mechanism 108 forproducing and scanning a visible laser beam across the bar code symbolon the detected object; photoreceiving circuit 109 for detecting laserlight reflected off the scanned bar code symbol and producing anelectrical signal D.sub.1 indicative of the detected intensity; aanalog-to-digital (A/D) conversion circuit 110 for converting analogscan data signal D.sub.1 into a corresponding digital scan data signalD.sub.2; a bar code presence detection circuit 111 for processingdigital scan data signal D.sub.2 in order to automatically detect thedigital data pattern of a bar code symbol on the detected object andproduce control activation signal A.sub.2=1; a third RC timing network112 for setting a timer T.sub.BCD in the bar code symbol detectioncircuit; second control means 113, realized as a second control circuitC.sub.2, for performing local system control operations in response tothe detection of the bar code symbol; third control means 114, realizedas third control module C.sub.3; a range selection, circuit 115 forsupplying range selection signals to the object detection circuit;second control circuit C.sub.2 and third control module C.sub.3; timersT.sub.2, T.sub.3, and T.sub.4 identified by reference numerals 116, 117and 118, respectively; a symbol decoding module 119 for processingdigital scan data signal D.sub.2 so as to determine the data representedby the detected bar code symbol, generate symbol character datarepresentative thereof, and produce activation control signal A.sub.3for use by third control module C.sub.3; a data packet, synthesis module120 for synthesizing a group of formatted data packets for transmissionto its mated base unit; and a data packet transmission circuit 121 fortransmitting the group of data packets synthesized by the data packetsynthesis module. As will be described in greater detail hereinafter,second control circuit C.sub.2 is capable of “overriding” (i.e., inhibitand/or enable) first control circuit C.sub.1, whereas third controlmodule C.sub.3 is capable of overriding first and second controlcircuits C.sub.1 and C.sub.2, respectively. As shown in FIG. 8, suchcontrol override functions are carried out by the generation of controloverride signals (i.e., C.sub.2/C.sub.1, C.sub.3/C.sub.2 andC.sub.3/C.sub.1) transmitted between respective control structures.Owing to the unique architecture of the control subsystem hereof, theautomatic bar code symbol reading device of the present invention iscapable of versatile performance and ultra-low power operation. Thestructure, function and advantages of this control subsystemarchitecture will become apparent hereinafter.

[0124] As shown in the schematic diagram of FIG. 8A, battery: powersupply unit 20 contained within the housing of the code symbol readingdevice provides electrical power to the components therewithin inaccordance with a programmed mode of intelligent operation. In theillustrative embodiment, battery power supply unit 20 comprises a powersupply distribution circuit 125, replaceable or rechargeable batteries126, and an automatic power control circuit 130. In the illustrativeembodiment, where; rechargeable batteries are employed, the power supplycircuit 20 further includes a secondary inductive coil 127, bridgerectifier 128 and voltage regulation circuit 129. Preferably, all ofthese, subcomponents are contained within the hand-supportable housingof the device, and are configured together as shown in FIG. 8A.

[0125] As illustrated in FIG. 8A, the function of second inductive coil128 is to establish an electromagnetic coupling with the primaryinductive coil contained in the base unit associated with the bar codereading device whenever the device is supported if in the rechargingportion of the base unit. In this configuration, electrical power isinductively transferred from the primary inductive coil in the base unitto secondary inductive coil 127, rectified by bridge rectifier 128, andfiltered by voltage regulation circuit 129 to provide a regulated DCpower supply for recharging rechargeable batteries 126.

[0126] As shown in FIG. 8A, automatic power control circuit 130 isconnected in series between rechargeable battery 126 and powerdistribution circuit 125. The function of automatic power controlcircuit 130 is to automatic control (i.e. manage) the availability ofbattery power to electrically-active components within the bar codesymbol reading device when the device is operated in its hands-on modeof operation (i.e. removed from the scanner support stand) under apredefined set of operating conditions. Notably while power distributioncircuit 125 distributes electrical power throughout the bar code symbolreading device by way of a power distribution bus, automatic powercontrol circuit 130 globally enables consumption of electrical power(i.e. the product of voltage and direct current) by the systemcomponents when activated.

[0127] As shown in FIG. 8A, the automatic power control circuit 130comprises a number of subcomponents, namely: a DC-to-DC voltageconverter 130A; a power commutation switch 130B; and a resettable timercircuit 130C. The function of the DC-to-DC voltage converter 103A is toconvert the voltage from battery power source 126 to +5 Volts, whereasthe function of the power commutation switch 130B is to selectivelycommute electrical power from the DC-to-DC converter 130A to the inputport of the power distribution circuit 125. The function of theresettable timer circuit 130C is to control the power commutationcircuit so that battery power is provided to the power distributioncircuit 125 in a power conserving manner without compromising theperformance of the bar code symbol reading system in its various modesof operation.

[0128] In the illustrative embodiment, DC-to-DC converter 130A isrealized by configuring a low-voltage input, adjustable output step-upDC-DC converter (e.g. such as the MAX777 IC chip by SLIM IntegratedProducts) with an inductor (e.g. 22.0 microHenries) and two capacitors,to produce a 5.0 Volt output voltage for use in the bar code symbolreading device. As shown, resettable timer circuit 130C is realized byconfiguring a comparator circuit 130C1 (e.g. as provided for example inthe LM2903 IC chip by National Semiconductor) with external resistorsR1, R2, R3, R4 and R5 and charging capacitor C1. The function of theresistors R3 and R5 is to provide to one inputs of the comparator apositive reference voltage (i.e. Vref) which is close in magnitude tothe battery voltage Vbattery, with resistor R4 being connected to theoutput of the comparitor for hysteresis. The power control switch 130Bis realized by N-channel field effect transistor (FET), wherein thesource terminal is connected to the output port of the DC-to-DCconverter 130A, the drain terminal is connector is connected to theinput port of the power distribution circuitry 125, and the gateterminal is connected to the output port of the comparitor 130C1.

[0129] In the illustrative embodiment, there are three different powerswitching events which will reset the resettable timer circuit 130C,cause the comparitor thereof to produce a high output level and drivethe N-channel FET into conduction. The first power switching eventcomprises manually depressing power reset button 130D mounted on theexterior of the scanner housing. The second power switching eventcomprises placing the handle portion of the scanner housing within therecess of the scanner support stand hereof, whereby Hall-effect sensor100 within the handle of the housing detects magnetic flux produced frompermanent magnet 103 within the scanner support stand recess, as shownin FIG. 1E. The third power switching event comprises successfullyreading a bar code symbol and producing activation signal A3=1.

[0130] In order that such power switching events will effectively resetthe resettable timer circuit 130C, a number of electrical devices areconnected to input port of the resettable timer circuit 130C,effectively realized by resistor R2. In particular, the “good read”activation signal A3=1 produced by symbol decoding module 119 isprovided to the base of a NPN transistor 130C2, which has its collectorterminal connected to one end of resistor R2 and its emitter terminalconnected to electrical ground. As shown, one terminal of manuallydepressible power reset button 130D (e.g. realized as a spring-biasedpush-type button switch) is connected to the same end of resistor R2, towhich the collector of NPN transistor 130C2 is connected, while theother terminal of power set button 130D is connected to electricalground. Also, one terminal of stand detector (e.g. Hall-effect sensor100) is connected to the same end of resistor R2, to which the collectorof NPN transistor 130C2 is connected, while the other terminal of theHall-effect sensor 100 is connected to electrical ground, as shown inFIG. 8A.

[0131] Battery supply 126 aboard the scanning device is automaticallycharged to its normal output voltage (i.e. Vbattery) by way of batteryrecharging apparatus 127, 128 and 129. A predetermined time duration.DELTA.T (e.g. 1 minute, preferably 5 minutes) after the occurrence of apower switching event, power supply unit 20 attains its steady-statecondition. At this state, capacitor C1 charges through resistor R1, to avoltage above Vref. This causes the output voltage of the capacitor130C1 to drop to a level which disables FET 130B, thereby disabling thesupply of battery power to power distribution circuit 125, andultimately disabling the scanning device. Upon the occurrence of any ofthe above three “power switching” events described above, capacitor C1quickly discharges through resistor R2 (i.e. R1>>R1), causing the outputvoltage of capacitor 130C1 to go to a level which enables FET 130B tosupply battery power to the power distribution circuitry 125, andthereby enabling the scanning device for the predetermined time period(e.g. .DELTA.T greater than 1, preferably 5 minutes). This programmedduration of power supply provides a time window .DELTA.T, within whichthe object detection circuit of the system hereof can automaticallydetect an object within the object detection field. Such power resettingoperation does not, however, initiate or otherwise cause laser scanningor bar code symbol reading operations to commence or cease. Only theintroduction of an object into the object detection field (i.e. when theresettable timer circuit 130C has been reset) can initiate or otherwisecause laser scanning or bar code symbol reading operations to commence.

[0132] A principal advantage of the power control scheme of the presentinvention is that it provides automatic power conservation in automaticcode symbol reading applications, while minimally impacting upon thediverse modes of automatic operation provided by the system hereof. Inparticular, provided that the user reads at least one bar code symbolwithin the predetermined time duration. DELTA.T programmed into the barcode symbol reading device, there is no need to reset the power controlcircuit hereor. Also, when the hand-supportable housing of the device isplaced (i.e. supported) within the support recess 60 of scanner supportportion of the base unit, Hall-effect sensor 103 produces a stand detectsignal which continuously causes power control circuit 130 to supplybattery power from continuously recharging battery 126, to the powerdistribution circuit 125, thereby enabling continuous scanner operationin the hands-free mode of operation.

[0133] Range selection circuit 115 may include a manual switchexternally accessible to the housing, which the user can depress toselect long or short-range modes of object detection, bar code presencedetection and/or bar code symbol reading. Alternatively, Range SelectionCircuit 115 can be activated to a particular range setting by symboldecoding module 119. In this mode of operation, the range setting can beset by decoding a bar code symbol predesignated to activate the long orshort range modes of detection, as the case may be.

[0134] In the illustrative embodiment of the present invention, primaryoscillator circuit 101, object detection circuit 107, first controlcircuit C.sub.1, analog-to-digital conversion circuit 110, bar codesymbol detection circuit 111, and second control circuit C.sub.2 are allrealized on a single Application Specific Integrated Circuit (ASIC) chip133 using microelectronic circuit fabrication techniques known in theart. In the illustrative embodiment, the ASIC chip and associatedcircuits for laser scanning and light detection and processing functionsare mounted on analog signal processing board 40. Symbol decoding module119, data packet synthesis module 120, timers T.sub.2, T.sub.3, T.sub.4,and T5 and third control module C.sub.3 are realized using a singleprogrammable device, such as a microprocessor having accessible programand buffer memory, and external timing circuitry, collectively depictedby reference numeral 134 in FIG. 8. In the illustrative embodiment,these components and devices are mounted on the PC board 50. In theillustrative embodiment, when power control switch 130 is in its reset(i.e. POWER ON) state, power from battery power unit 126 is provided tofirst control circuit C.sub.1, priffary, oscillator circuit 101 and IRobject sensing circuit 106 and object detection circuit 107 so as toenable their operation, while only biasing voltages are provided to allother system components so that they are each initially disabled fromoperation. When power control switch 130 is in its POWER OFF state,power from battery power unit 126 is not commuted to power distributioncircuit 125, and thus not provided to any components in the system. Aswill be described in greater detail hereinafter, provision of electricalpower to all other system components occurs under the management of thecontrol architecture formed by the interaction of distributed controlcenters C.sub.1, C.sub.2 and C.sub.3.

[0135] As shown in FIG. 8, primary clock oscillator circuit 101 suppliesa periodic pulsed signal to both the system override signal detectioncircuit and the object detection circuit. In the illustrativeembodiment, the primary oscillation circuit is designed to operate at alow frequency (e.g., about 1.0 Khz) and a very low duty cycle (e.g.,about 1.0%). The “ON” time for the system override signal producingmeans and the IR object sensing circuit is proportional to the dutycycle of the primary oscillation circuit. This feature allows forminimal operating current when the bar code symbol reading device is inthe object detection mode and also when the system override signalproducing device is activated (i.e., produces a system override signal).

[0136] As shown in FIG. 8B, primary oscillation circuit 101 comprises aSchmidtt trigger 142, invertors 143 and 144, and a NMOS Field-EffectTransistor (FET) 145. As shown, the output of trigger 142 is connectedto the inputs of both invertors 143 and 144. The output of invertor 143produces clock signal CLK which is provided to system override signaldetection circuit 100 and object detection circuit 107. The primaryoscillation circuit is connected to first RC network 102 which comprisesresistors R.sub.1 and R.sub.2, and capacitor C.sub.1 configured as shownin FIG. 8B. The function of the RC network 102 is to establish the dutycycle and the oscillation period of the primary oscillator circuit. Asshown, two time constants (i.e., loads) are established by the networkusing capacitor C.sub.1 and resistors R.sub.1 and R.sub.2. The RCcombination of R.sub.1 and C.sub.1 establishes the period of theoscillator. The ratio of the R.sub.2 to R.sub.1 provides the duty cycleof the oscillator. The value of R.sub.2 is approximately 100 timessmaller than R.sub.1 to establish a 1.0% duty cycle. As shown in thetiming diagram of FIG. 8C, the clock signal CLK remains low while theV.sub.1=1 signal ramps up. This ramp up time is the time it takes forthe capacitor C.sub.1 to charge through R.sub.1. The clock signal CLKthen goes HIGH for the shorter discharge time of the capacitor throughR.sub.2. By adjusting the duty cycle (i.e., increasing or decreasing thevalue of resistor R.sub.2), the sensitivity of the object detectioncircuit can be tuned such that it activates consistently at a specifieddistance from the light transmission a window of the bar code symbolreading device.

[0137] In accordance with the present invention, the purpose of objectdetection circuit 107 is to produce a first control activation signalA.sub.1=1 upon determining that an object (e.g., product, document,etc.) is present within the object detection field of the bar codesymbol reading device, and thus at least a portion of the scan fieldthereof. As illustrated in FIG. 8, the object detection circuit isactivated (i.e., enabled) by enabling, signal E.sub.0 supplied fromfirst control circuit C.sub.1, and the object detection circuit providesthe first control circuit C.sub.1 with first control activation signalA.sub.1=1 when an object residing in the scan field is detected. In theillustrative embodiment, an “active” technique of automatic objectdetection is employed, although it is understood that “passive”techniques may be used with acceptable results. As shown in FIG. 8, theobject detection means of the system comprises two major subcomponents,namely object sensing circuit 106 and object detection circuit 107, bothof which are locally controlled by control circuit C.sub.1. In theillustrative embodiment, object sensing circuit comprises an IR LED 148driven by an IR transmitter drive circuit 149, and an IR phototransistor(or photodiode) 150 activated by an IR receive biasing circuit 151. Asshown in FIGS. 7D and 7F, these components are arranged and mounted onPC board 41 so as to provide an object detection field that spatiallyencompasses the laser scanning plane, as described above. As shown inFIG. 8, the object detection circuit 107 produces an enable signal IR DRwhich is provided to the IR transmitter drive circuit 149. The signalproduced from IR phototransistor 151, identified as IR REC, is providedas input signal to the object detection circuit 107 for signalprocessing in a manner which will be described in detail below. In theillustrative embodiment, infrared LED 148 generates a 900 nanometersignal that is pulsed at the rate of the primary oscillation circuit 101(e.g., 1.0 KHZ) when the object detection circuit is enabled by enablesignal E.sub.0 produced from the first control circuit C.sub.1.Preferably, the duty cycle of the primary oscillation circuit 101 isless than 1.0% in order to keep the average current consumption verylow.

[0138] As shown in FIG. 3A, in particular, this pulsed optical signal istransmitted from infrared LED 148 to broadly illuminate the scan field.When an object is present within the object detection portion of thescan field, a reflected optical pulse signal is produced and focussedthrough focusing lens 153 onto photodiode 150. The function ofphotodiode 150 is to receive (i.e., sense) the reflected optical pulsesignal and, in response thereto, produce a current signal IR REC.

[0139] As shown in FIG. 8D, produced current signal IR RE (is providedas input to the current-to-voltage amplifier (e.g., transconductanceamplifier) 155 in the object detection circuit, and is converted into avoltage signal Vo. Within the object detection circuit 107, theinfra-red LED drive signal IR DR is produced as the output of AND gate157, whose inputs are enabling signal E.sub.0 supplied from the firstcontrol circuit C.sub.1 and the pulsed clock signal CLK supplied fromthe primary oscillation circuit 101.

[0140] As shown in FIG. 8D, enabling signal E.sub.0 is also provided tocurrent-to-voltage amplifier circuit 155, and the output voltage signalfrom AND gate 157 is provided as the second input to the synchronoustransmitter/receiver circuit 156. Notably, the output voltage signalfrom AND gate 157 and the output voltage signal V.sub.0 from thecurrent-to-voltage amplifier correspond to the IR pulse signal trainstransmitted from and received by object sensing circuit 106. Thefunction of the synchronous transmitter/receiver circuit is tocyclically compare the output voltage signal from AND gate 157 and theoutput voltage signal V.sub.0 from the current-to-voltage amplifier, andif these voltage signals synchronously match each other for a minimum ofthree (3) consecutive cycles of the primary oscillation circuit 101,then synchronous transmitter/receiver circuit 156 produces as output, afirst control activation signal A.sub.1=1, indicative that an object ispresent in the scan field of the bar code symbol reading device.Conversely, whenever first control activation signal A.sub.1=0 isproduced, then this condition indicates that an object is not present inthe scan field.

[0141] Alternatively, the automatic bar code reading device of thepresent invention can be readily adapted to sense ultrasonic energyreflected off an object present within the scan field. In such analternative embodiment, object sensing circuit 106 is realized as anultrasonic energy transmitting/receiving mechanism. In the housing ofthe bar code reading device, ultrasonic energy is generated andtransmitted forwardly into the scan field. Then, ultrasonic energyreflected off an object within the object detection field is detectedadjacent to the transmission window using an ultrasonic energy detectorthat produces an analog electrical signal (i.e., UE REC) indicative ofthe detected intensity of received ultrasonic energy. Preferably, afocusing element is disposed in front of the energy detector in order toeffectively maximize the collection of ultrasonic energy reflected offobjects in the scan field. In such instances, the focusing elementessentially determines the geometrical characteristics of the objectdetection field of the device. Consequently, the energy focusing (i.e.,collecting) characteristics of the focusing element will be selected toprovide an object detection field which spatially encompasses at least aportion of the scan field. The electrical signal produced from theultrasonic-energy based object sensing circuit is provided to objectdetection circuit 107 for processing in the manner described above.

[0142] In the illustrative embodiment, object detection circuit 107 isprovided with two different modes of detection, namely, a long-rangemode of object detection and a short-range mode of object detection. Asshown in FIGS. 8 and 8D, these modes are set by range selection circuit115 using mode enable signal R.sub.1. When induced into the long-rangemode of object detection, object detection circuit 107 will generatefirst control activation signal A.sub.1=1 whenever an object has beendetected within the operative range of the object detection field,independent of the particular distance at which the object resides fromthe transmissive window. When induced into the short-range mode ofobject detection, the object detection circuit will generate firstactivation control signal A.sub.1=1 only when an object is detected at adistance within the short-range of the object detection field.

[0143] As schematically indicated in FIGS. 2 and 2A, the long-rangespecification for object detection is preferably preselected to be thefull or entire range of sensitivity provided by current-to-voltageamplifier (e.g., 0 to about 10 inches). Preferably, the short-rangespecification for object detection is preselected to be the reducedrange of sensitivity provided by the IR sensing circuit when mode enablesignal E.sub.IRT=1 is provided to the desensitization port of amplifier155. In the illustrated embodiment, the short-range of object detectionis about 0 to about 3 inches or so to provide CCD-like scanneremulation. As will become apparent hereinafter, the inherently limiteddepth and width of field associated with the short-range mode of objectdetection prevents laser scanning mechanism 108 from flooding the scanfield with laser scanning light and thus inadvertently detectingundesired bar code symbols. Particular uses to which object detectionrange selection can be put, will be described in greater detailhereinafter.

[0144] As shown in FIG. 8D, the sensitivity (i.e., gain) ofcurrent-to-voltage amplifier 155 is controlled by a sensitivity controlsignal E.sub.IRT produced from range control signal generating circuit158. In the illustrative embodiment, the sensitivity control signalE.sub.IRT 160 is produced by a resistance network whose values areselected using an analog switch that is responsive to a range selectsignal R.sub.1 produced by range selection circuit 115. As such, thesensitivity of the current-to-voltage amplifier is simply adjusted byselecting one of two resistance values within the resistance networkused to realize range control signal generating circuit 158. The shortrange mode of object detection is enabled by selecting a resistancevalue that produces an amplifier gain that is lower than that producedduring the long-range mode, of object detection where detectable objectscan reside further away from the light transmission window of the barcode symbol reading device.

[0145] In general, first control logic block C.sub.1 provides the firstlevel of system control. This control circuit activates the objectdetection circuit 107 by generating enable signal E.sub.0=1, ittactivates laser beam scanning circuit 108, photoreceiving circuit 109and A/D conversion circuit 110 by generating enable signal E.sub.1=1,and it activates bar code symbol detection circuit 111 by generatingenable signal E.sub.2=1. In addition, the first control circuit C.sub.1provides control lines and signals in order to control these functions,and provides a system override function for the low power standby modeof the bar code symbol reading device. In the illustrative embodiment,the specific operation of first control circuit C.sub.1 is dependent onthe state of several sets of input signals (i.e., activation controlsignal A.sub.0 and A.sub.1, and override signals C.sub.2/C.sub.1,C.sub.3/C.sub.1−1 and C.sub.3/C.sub.1−2) and an internally generateddigital timer signal B. A preferred logic implementation of the firstcontrol circuit C.sub.1 is set forth in FIGS. 8E and 8F. The functionaldependencies among the digital signals in this circuit are representedby the Boolean logic expressions set forth in the Table of FIG. 8G, andtherefore are sufficient to uniqutely characterize the operation offirst control circuit C.sub.1.

[0146] As shown in FIG. 8E, first control circuit comprises a pair oflogic invertors 161 and 162, a NAND gate 164, a NOR gate 165, an ANDgate 166, and a digital timer circuit 167 which produces as output, adigital output signal B. As shown, digital timer circuit 167 comprises aflip-flop circuit 170, a NOR gate 171, a clock divide circuit 173, acomparator (i.e., differential) amplifier 172, and a NPN transistor 174.As illustrated, activation control signal A.sub.1 is provided to the CLKinput of flip-flop 170 by waly of invertor 161. The QNOT output of theflip-flop is provided as one input to NOR gate 171, whereas the otherinput thereof is connected to the CLK input of clock divide circuit 173and the output: of comparator amplifier 172. The output of the NOR gateis connected to the base of transistor 174, while the emitter thereof isconnected to electrical ground and the collector is connected to thenegative input of comparator amplifier 172 as well as the second timingnetwork 105, in a manner similar to the interconnection of first timingnetwork 102 to primary oscillation circuit 101. Also, the divided clockoutput (i.e., CLK/2048) produced from clock divide circuit 173 isprovided to the CL input of flip-flop 170. As shown, the Q output offlip-flop 170 is connected to the reset (RST) input of the clock dividecircuit 173 as well as to one input of NAND gate 164, one input of NORgate 165, and one input of AND gate 166. Notably, the Q output of theflip-flop is the digital output signal B indicated in each of theBoolean expressions set forth in the Table of FIG. 8G.

[0147] As shown in FIG. 8E, the override signal C.sub.2/C.sub.1 fromsecond control circuit C.sub.2 is provided as the input to invertor 162,whereas the output thereof is provided as the second input to AND gate166. The override signal C.sub.3/C.sub.1−1 from third control moduleC.sub.3 is provided as the second input to NAND gate 164, whereas theoutput thereof produces enable signal E.sub.0 for activating the objectdetection circuit 107. The override signal C.sub.3/C.sub.1=2 is providedto the second input to NOR gate 165, whereas the output thereof producesenable signal E.sub.1 for activating laser scanning and photoreceivingcircuits 108 and 109 and A/D conversion circuit 110. The output of ANDgate 166 produces enable signal E.sub.2 for activating bar code symboldetection circuit 111.

[0148] Referring to FIG. 8E, the operation of digital timer circuit willbe described. The output voltage of comparator amplifier 172 keepstransistor 174 in its non-conducting state (i.e., OFF), via NOR gate171, thus allowing the external RC network 105 to charge to capacity.When comparator input voltage Vx exceeds reference voltage VCC/2, thecomparator output voltage biases (i.e., switches ON) transistor 174 soas to begin discharging the RC timing network 105, until input voltageVx falls below reference voltage VCC/2 upon which the process repeats,thus generating a digital clock oscillation at the comparator output.The timing cycle of digital output signal B is initiated by a transitionon the activation control signal A, which toggles flip-flop 170. Thistoggling action sets the digital output signal B to its logical HIGHstate, resetting clock divide circuit 173 and starting the digitalclocks oscillator described above by toggling the Q output of flip-flop170. As shown in FIG. 8F, clock divide circuit 173 is constructed bycascading eleven flip-flop circuits together in a conventional manner.Each stage of the clock divider circuit divides the input clock signalfrequency by the factor 2. Thus the clock divider circuit provides anoverall division factor of 2048. When the clock output CLK/2048 toggles,the flip-flop circuit is cleared thus setting the digital signal B tological LOW until the next pulse of the activation control signalA.sub.1.

[0149] As reflected in the Boolean expressions of FIG. 8G, the state ofeach of the enable signals E.sub.0, E.sub.1 and E.sub.2 produced by thefirst control circuit C.sub.1 is dependent on whether the bar codesymbol reading system is in its override state of operation. To better,understand the operation of control circuit C.sub.1, it is helpful toconsider a few control strategies preformed thereby.

[0150] In the override state of operation of the system, enable signalE.sub.0 can be unconditionally set to E.sub.0=0 by the third controlcircuit C.sub.3 setting override signal C.sub.3/C.sub.1=0. Under suchconditions, the object detection circuit is enabled. Also, when thelaser scanning and photoreceiving circuits are activated (i.e., B=1) andoverride signal C.sub.3/C.sub.1−1=1, then enable signal E.sub.0=1 andtherefore the object detection circuit is automatically deactivated. Theadvantage of this control strategy is that it is generally not desirableto have both the laser scanning circuit 108 and photoreceiving circuit109 and the object sensing circuit 105 active at the same time, as thewavelength of the infrared LED 148 typically falls within the opticalinput spectrum of the photoreceiving circuit 109. In addition, lesspower is consumed when the object detection circuit 107 is inactive(i.e., disabled).

[0151] As illustrated in FIG. 8, laser scanning circuit 108 comprises asolid-state visible laser diode (VLD) 177 driver, by a conventionaldriver circuit 178. In the illustrative embodiment, the wavelength ofvisible laser light produced from the laser diode is preferably about670 nanometers. In order to repeatedly scan the produced laser beam overthe scanning volume, the rotating polygon is rapidly accelerated tooperating speed by motor 37 driven by a conventional driver circuit 181,as shown. Stationary mirror 44 directs the laser beam from the laserdiode to the rotating polygon. To selectively activate both laser lightsource 38 and motor 37, a laser diode and scanning motor enable signalE.sub.1 provided as input to driver circuits 178 and 181. When enable itsignal E.sub.1 is a logical “high” level (i.e., E.sub.1=1) a laser beamis generated and projected through the light transmissive window, whenthe projected laser beam is repeatedly scanned through the scanningvolume, and an optical scan data signal is thereby produced off theobject (and bar code) residing within the scanning volume. When a laserdiode and scanning motor enable signal E.sub.1 is a logical “low” (i.e.,E.sub.1=0), there is no laser beam produced, projected, or scannedacross the scanning volume.

[0152] When a bar code symbol is present on the detected object at thetime of scanning, the visible laser beam is automatically scanned acrossthe bar code symbol within the 3-D scanning volume, and incident laserlight on the bar code symbol will be scattered and reflected. Thisscattering/reflection process produces a laser light return signal ofvariable intensity which represents a spatial variation of lightreflectivity characteristic of the pattern of bars and spaces comprisingthe bar code symbol. Photoreceiving circuit 109 detects at least aportion of the reflected laser light of variable intensity and producesan analog scan data signal Dindicative of the detected light intensity.

[0153] In the illustrative embodiment, photoreceiving circuit 109generally comprises a number of components, namely: laser lightcollection optics (i.e., stationary mirror array 38 and focusing mirror43) for focusing reflected laser light for subsequent detection;photoreceiver 41 (e.g., a silicon photosensor) mounted onto PC board 40,as shown in FIG. 5D, for detecting laser light focused by the lightcollection optics; and frequency selective filter 186A, mounted in frontof photoreceiver 41, for transmitting thereto only optical radiationhaving wavelengths up to a small band above 670 nanometers.

[0154] In order to prevent optical radiation slightly below 670nanometers from passing through light transmission aperture 12A andentering the housing, the light transmissive window 68 realized as aplastic filter lens is installed over the light transmission aperture ofthe housing. This plastic filter lens has optical characteristics whichtransmit only optical radiation from slightly below 670 nanometers. Inthis way, the combination of plastic filter lens 12 at the transmissionaperture and frequency selective filter 186A before photoreceiver 41cooperate to form a narrow band-pass optical filter having a centerfrequency f.sub.c=670 nanometers. By permitting only optical radiationassociated with the visible laser beam to enter the housing, thisoptical arrangement provides improved signal-to-noise ratio for detectedscan data signals D.sub.1. This novel filtering optical arrangement isdisclosed in greater detail in copending application Ser. No.08/439,224, supra.

[0155] In response to reflected laser light focused onto photo receiver41, photoreceiver 41 produces an analog electrical signal which isproportional to the intensity of the detected laser light. This analogsignal is subsequently amplified by preamplifier 187 to produce analogscan data signal D.sub.1. In short, laser scanning circuit 108 andphotoreceiving circuit 109 cooperate to generate analog scan datasignals D.sub.1 from the scan field, over time intervals specified byfirst control circuit C.sub.1 during normal modes of operation, and bythird control module C.sub.3 during “control override” modes ofoperation.

[0156] As illustrated in FIG. 8, analog scan data signal D.sub.1 isprovided as input to A/D conversion circuit 110, shown in FIG. 8H. In amanner well known in the art, A/D conversion circuit 110 processesanalog scan data signal D.sub.1 to provide a digital scan data signalD.sub.2 which has a waveform that resembles a pulse width modulatedsignal, where logical “1” signal levels represent spaces of the scannedbar code and logical “0” signal levels represent bars of the scanned barcode. A/D conversion circuit 110 can be realized using any conventionalA/D conversion techniques well known in the art. Digitized scan datasignal D.sub.2 is then provided as input to bar code presence detectioncircuit 111 and symbol decoding module 119 for use in performingparticular functions required during the bar code symbol reading processof the present invention.

[0157] The primary purpose of bar code presence detection circuit 111 isto determine whether a bar code is present in or absent from the scanfield, over time intervals specified by first control circuit C.sub.1during normal modes of operation and by third control module C.sub.3during control override modes of operation. In the illustrativeembodiment, bar code presence detection circuit 111 indirectly detectsthe presence of a bar code in the narrowly-confined scanning volume 13by detecting its bar code symbol “envelope”. In the illustrativeembodiment, a bar code symbol envelope is deemed present in the scanningvolume upon detecting a corresponding digital pulse sequence in digitalsignal D.sub.2 that A/D conversion circuit 110 produces whenphotoreceiving circuit 109 detects laser light reflected off a bar codesymbol scanned by the laser beam produced by laser beam scanning circuit108. This digital pulse sequence detection process is achieved bycounting the number of digital pulse transitions (i.e., falling pulseedges) that occur in digital scan data signal D.sub.2 within apredetermined time period T.sub.1 clocked by the bar code symboldetection circuit. According to the laws of physics governing the laserscanning operation, the number of digital (pulse-width modulated) pulsesdetectable at photoreceiver 41 during time period T.sub.1 is a functionof the distance of the bar code from the light transmission window 12 atthe time of scanning. Thus a bar code symbol scanned at 6″ from thelight transmission window will produce a larger number of digital pulses(i.e., digital count) at photoreceiver 41 during time period T.sub.1than will the same bar code symbol scanned at 3″ from the lighttransmission window.

[0158] In the illustrative embodiment, the bar code symbol detectioncircuit 111 is provided with the capacity to detect the presence of abar code symbol in either the long or short range portions of thescanning volume, as specified in FIGS. 3 and 3A. This is achieved bycounting the digital pulse transitions present in digital scan signalD.sub.2 within predetermined time period T.sub. and producing secondcontrol activation signal A.sub.2S (i.e., A.sub.2S=1) when the countednumber of pulse transitions equals or exceeds a first prespecifieddigital pulse transition count corresponding to a bar code symbolscanned in the short range portion of the scan field, and producingsecond control activation signal A.sub.2L (i.e., A.sub.2L=1) when thecounted number of pulse transitions equals or exceeds a secondprespecified digital pulse transition count corresponding to a bar codesymbol scanned in the long range portion of the scanning volume. Asshown in FIG. 8, both of these second control activation signalsA.sub.2L and A.sub.2S are produced and provided as input to secondcontrol circuit C.sub.2. However, second control circuit C.sub.2selectively provides (e.g., gates) the second control activation signalthat corresponds to range-mode of operation selected by the user. Whenthe long range mode of operation has been selected by range selectioncircuit 115, the device will automatically undergo a transition from barcode presence detection state to bar code symbol reading state uponreceiving control activation signal A.sub.2L=1. Similarly, when theshort range mode of operation has been selected by the range selectioncircuit 115, the device will automatically undergo a transition from barcode presence detection state to bar code symbol reading state uponreceiving control activation signal A.sub.2S=1.

[0159] In the illustrative embodiment, bar code symbol presencedetection circuit 111 comprises a digital pulse transition counter 190for counting digital pulse transitions during time period T.sub.1, and adigital clock circuit (i.e., T.sub.BCD circuit) 191 for measuring (i.e.,counting) time period T.sub.BCD and producing a count reset signal CNTRESET at the end of each such time period, as shown in FIG. 8K. As shownin FIG. 8K, the function of digital clock circuit 191 is to provide atime period T.sub.BCD (i.e., time window subdivision) within which thebar code symbol detection circuit attempts, repeatedly during timeperiod T.sub.1, to detect a bar code symbol in the scan field. In thepreferred embodiment, T.sub.BCD is about 0.1 seconds, whereas T.sub.1 isabout 1.0 second. As shown in FIG. 8I, in order to establish such “barcode search” time it subintervals within time period T. sub.1, thedigital clock circuit 191 generates the first count reset pulse signalCNT RESET upon the detection of the first pulse transition in digitalscan data signal D.sub.2. The effect of this reset signal is to clear orreset the digital pulse transition (falling edge) counter. Then at theend of each time subinterval T.sub.BCD, digital clock signal 191generates another count reset pulse CNT RESET to reset the digital pulsetransition counter. If during time window T.sub.1, a sufficient numberof pulse transitions in signal D.sub.2 are counted over a subintervalT.sub.BCD, then either control activation signal A.sub.2L or A.sub.2S,will be set to “1”. In response to the detection of this condition,second control circuit C.sub.2 automatically enables control activationC.sub.3 in order to initiate a transition from the bar code symboldetection state of operation to the bar code symbol reading state ofoperation.

[0160] As shown in FIG. 8I, digital pulse transition counter 191 isformed by wiring together a series of four flip-flop circuits 192 to195, such that each flip flop divides the clock signal frequency of theprevious stage by a factor of 2. As indicated in the drawing of FIG. 8I,the Q output of flip flops 192 to 194 represent the binary digits 2, 4,8, and 16 respectively, of a binary number (i.e., counting) system. Asshown, enable signal E.sub.2 from first control circuit C.sub.1 isprovided as input to NOR gate 197, while the second input thereto is thecounter reset signal CNT RESET provided from the digital counter circuit191. In order to reset or clear the pulse transition counter circuit 190upon the generation of each CNT RESET pulse, the output of the NOR gate197 is connected to the clear line (CL) of each flip flop 192 to 195, asshown.

[0161] As illustrated in FIG. 8, digital clock circuit 191 comprises aflip-flop circuit 198, a NOR gate 199, a clock divide circuit 200, acomparator 201, and a NPN transistor 202. As illustrated, digital scandata signal D.sub.2 is directly provided to the CLK input of flip-flop198. The QNOT output of the flip-flop is provides as one input to NORgate 199, whereas the Q output thereof is connected to the CLK input ofclock divide circuit 200 and the second input of NOR gate 197. The otherinput of NOR gate 199 is connected to the input line CLK of clock dividecircuit 200 and to the output of comparator 201, as shown. The output ofthe NOR gate is connected to the base of transistor 202, while theemitter thereof is connected to electrical ground and the collector isconnected to the negative input of comparator 201 as well as to thethird timing network 112, in a manner similar to the interconnection ofthe first timing network 102 to primary oscillation circuit 101. Asshown in FIG. 8J, clock divide circuit 200 is realized as series of fiveflip-flops 200A to 200E wired together so as to divide digital clockinput signal CLOCK by 32, and be resettable by pulsing reset line RESETin a conventional manner.

[0162] When an object is detected in the scan field, first controlcircuit C.sub.1 produces enable signal E.sub.2=1 so as to enable digitalpulse transition counter 190 for a time duration of T.sub.1. As shown,the digital scan data signal D.sub.2 (representing the bars and spacesof the scanned bar code) drives the clock line of first flip flop 192,as well as the clock line of flip flop 198 in the T.sub.BCD timercircuit. The first pulse transition in digital scan data signal D.sub.2starts digital timer circuit 191. The production of each count resetpulse CNT RESET from digital timer circuit 191 automatically clears thedigital pulse transition counter circuit 190, resetting it once again tocount the number of pulse transitions present in the incoming digitalscan data signal D.sub.2 over a new time subinterval T.sub.BCD. The Qoutput corresponding to eight pulse transitions counted during timeperiod TBCD, provides control activation signal A.sub.2 S for use duringthe short range mode of operation. The Q output corresponding to sixteenpulse transitions counted during time period T.sub.BCD, provides controlactivation signal A.sub.2L for use during the long range mode ofoperation. When the presence of a bar code in the scan field isdetected, second activation control signal A.sub.2L or A.sub.2S isgenerated, third control circuit C.sub.3 is activated and second controlcircuit C.sub.2 is overridden by third control circuit C.sub.3 throughthe transmission of control override signals (i.e., C.sub.3/C.sub.2inhibit and C.sub.3/C.sub.1 enable signals) Prom the third controlcircuit C.sub.3.

[0163] As illustrated in FIG. 8L, second control circuit C.sub.2 isrealized using logic circuitry consisting of NAND gates 205 to 208,invertors 209 and 210, NOR gates 211 to 213, NAND gates 214 and 215, ANDgate 216, configured together as shown. As shown, second controlactivation signals A.sub.2S. and A.sub.2L are provided to the firstinputs of NAND gates 214 and 215, respectively, whereas the outputs ofNOR gates 211 and 212 are provided to the second inputs of NAND gates214 and 215 respectively. The outputs of NAND gates 214 and 215 areprovided to the inputs of AND gate 216 and the output thereof providesenable signal E.sub.3 for enabling third control module C.sub.3.

[0164] As shown in FIG. 8L, the third control module C.sub.3 providesoverride signals C.sub.3/C.sub.2−1 and C.sub.3/C.sub.2−2 to the firstand second inputs of NAND gate 205 and to the first input of NAND gate207 and the first input of NAND gate 208, respectively. The rangeselection signal R produced from range selection circuit 115 is providedas input to NAND gate 206. As shown, output of NAND gate 205 is providedas the second input to NAND gate 206. The output of NAND gate 206 isprovided as the second input to NAND gate 207 and the, second input toNAND gate 208. As shown in FIG. 8L, the output of NAND gate 207 isprovided as an input to NOR gate 211 and invertor 209, whereas theoutput of NAND gate 208 is provided as inputs to NOR gates 211 and 212and invertor 210. The output of invertor 209 is provided as the otherinput to NOR gate 212 and one input to NOR gate 213. The output ofinvertor 210 is provided as another input to NOR gate 213, whereas theoutput thereof provides control override signal C.sub.2/C.sub.1. Soconfigured, the combinational logic of the second control circuitC.sub.2 maps its input signals to its output signals in accordance withthe logic table of FIG. 8M.

[0165] Upon entering the bar code symbol reading state, third controlmodule C.sub.3 provides override control signal C.sub.3/C.sub.1 to firstcontrol circuit C.sub.1 and second control circuit C.sub.2. In responseto control signal C.sub.3/C.sub.1, the first control circuit C.sub.1produces enable signal E.sub.1=1 which enables scanning circuit, 109photo-receiving E circuit 109 and A/D conversion circuit 110. Inresponse to control signal C.sub.3/C.sub.2, the second control circuitC.sub.2 produces enable signal E.sub.2=0, which disables bar code symboldetector circuit 111. Thereafter, third control module C.sub.3 producesenable signal E.sub.4 to enable symbol decoding module 119. In responseto the production of such signals, the symbol decoding module decodeprocesses, scan line by scan line, the stream of digitized scan datacontained in signal D.sub.2 in an attempt to decode the detected barcode symbol within the second predetermined time period T.sub.2established and monitored by the third control module C.sub.3. If thesymbol decoding module 119 successfully decodes the detected bar codesymbol within time period T.sub.2, then symbol character data D.sub.3(representative of the decoded bar code symbol and typically in ASCIIcode format) is produced. Thereupon symbol decoding module 119 producesand provides the third control activation signal A.sub.3 to the thirdcontrol module C.sub.3 in order to induce a transition from the bar codesymbol reading state to the data packet transmission state. In responsethereto, a two distinct events occur. First the third control moduleC.sub.3 produces and provides enable signal E.sub.5 to data packetsynthesis module 120. Secondly, symbol decoding module 119 stores symbolcharacter data D.sub.3 in a memory buffer associated with data packetsynthesis module 120.

[0166] In the illustrative embodiment, symbol decoding module 119, datapacket synthesis module 120, and timers T.sub.2, T.sub.3, T.sub.4 andT.sub.5 are each realized using programmed microprocessor and accessiblememory 134. Similarly, third control module C.sub.3 and the controlfunctions which it performs at Blocks to GG in FIGS. 13A and 13C, arerealized as a programming implementation using techniques well known inthe art.

[0167] The function of data packet synthesis module 120 is to use theproduced symbol character data to synthesize a group of data packets forsubsequent transmission to its assigned base unit by way of data packettransmission circuit 121.

[0168] In the illustrative embodiment, each synthesized data packet isformatted as shown in FIG. 8N. In particular, each data packet in eachdata packet group comprises a number of data fields, namely: Start ofPacket Field 220 for containing a digital code indicating the beginningof the transmitted data packet; Transmitter Identification Number Field221 for containing a digital code representative of the Transmitting BarCode Symbol Reader; Data Packet Group Number Field 222 for containing adigital code (i.e., a first module number) assigned to each particulardata packet group being transmitted; Data Packet Transmission No. Field223 for containing a digital code (i.e., a second module number)assigned to each data packet in each data packet group beingtransmitted; Symbol Character Data Field 224 for containing digital coderepresentative of the symbol character data being transmitted to thebase unit; Error Correction Code Field 225 for containing a digitalerror correction code for use by the receiving base unit to determine iferror in data packet transmission has occurred; and End of Packet Fieldfor 226 for containing a digital code indicating the end of thetransmitted data packet.

[0169] After the data packet synthesis module synthesizes a group ofdata packets as described above, the third control module C.sub.3provides enable signal E.sub.7 to data packet transmission circuit 121.As illustrated in FIG. 9, the data packet transmission circuit comprisesa carrier signal generation circuit 230, a carrier signal frequencymodulation circuit 231, a power amplifier 232, a matching filter 233,and a quarterwave (¼) transmitting antenna element 234. The function ofthe carrier signal generation circuit 2303 is to generate a carriersignal having a frequency in the RF region of the electromagneticspectrum. In the illustrative embodiment, the carrier frequency is about912 Mhz, although it is understood that this frequency may vary from oneembodiment of the present invention, to another embodiment thereof. Asthe carrier signal is being transmitted from transmitting antenna 234,frequency modulation circuitry 231 modulates the instantaneous frequencyof the carrier signal using the digital data sequence (i.e., digitaldata stream) 235 constituting the group of data packets synthesized bythe data packet synthesis module 120. The function of the poweramplifier is to amplify the power of the transmitted modulated carriersignal so that it may be received by a base unit of the presentinvention located within a predetermined data transmission range (e.g.,from about 0 to about 30 feet).

[0170] In general, each base unit of the present invention performs anumber of functions. First, the base unit receives the modulated carriersignal transmitted from a hand-supportable bar code symbol readingdevice within the data reception range of the base unit. Secondly, thebase unit demodulates the received carrier signal to recover the datapacket modulated thereunto during signal transmission. Thirdly, the baseunit analyzes each of the recovered data packets to determine whetherthe received carrier signal was transmitted from a hand-supportable barcode symbol reading device preassigned to the receiving base unit.Fourthly, the base unit recovers the symbol character data from at leastone data packet in a transmitted group of data packets, and ascertainingthe reliability of the recovered symbol character data. Fifthly, thebase unit generates an acoustical acknowledgement signal SACK that canbe audibly perceived by the operator of the transmitting bar code symbolreading device while located in the data reception range of the baseunit. Finally, the base unit transmits the received symbol characterdata to a host computer system or like device. Each of these functionswill be described in greater detail during the detailed description ofthe Main System Control Routine set forth in FIGS. 13A to 13C.

[0171] In order to better understand the functions performed by the barcode symbol reading device and base unit of the present invention, itwill be helpful to first describe the principles underlying the datacommunication method of the present invention, and thereafter discussthe role that the base unit plays in carrying out this communicationmethod.

[0172] In general, one or more bar code symbol reading devices can bemated (i.e. registered or assigned) to operate with a single base unit3. In a first illustrative embodiment of the present invention, each barcode symbol reading device is a (resultant) system of bar code symbolreading subsystems installed in physical proximity with each other.Typically, each system is a point of sale (POS) station comprising (i) ahost computer system interfaced with a base unit of the presentinvention and (ii) an automatic hand-supportable bar code symbol readingdevice preassigned to one of the base units. In such an illustrativearrangement, each bar code symbol reading device is mated (i.e.registered or associated) with a single base unit by storing a unique,preassigned “Transmitter Identification Code” in a memory device withinthe assigned base unit during a set-up procedure.

[0173] In the illustrative embodiment, the carrier frequency of the datapacket transmitter in each bar code symbol reading device issubstantially the same for all bar code symbol reading devices in theresultant system. Also, the data packet transmission range of each barcode symbol reading device will be substantially greater than thedistance between each bar code symbol reading device and a neighboringbase unit to which the bar code symbol reading unit is not assigned.Consequently, under such operating conditions, at any instance in time,any base station in the resultant system may simultaneously receive twoor more packet modulated carrier signals which have been transmittedfrom two or more bar code symbol reading devices being used in theresultant system. These bar code symbol reading devices may include thebar code symbol reading device preassigned to the particular base unitas well as neighboring bar code symbol reading devices. Thus due to theprinciples of data packet transmission of present invention, thereexists the possibility that any particular base unit may simultaneouslyreceive two or more different data packets at any instant in time,thereby creating a “packet interference” situation.

[0174] In order to ensure that each base unit in the resultant system iscapable of receiving at least one data packet from a data packet grouptransmitted by its preassigned bar code symbol reading device (i.e.,without risk of interference from neighboring bar code symbol readingdevice transmitters), the unique “data packet group” transmission schemeshown in FIG. 10 is employed. As shown, upon the successful reading of afirst bar code symbol and the production of its symbol character dataD.sub.3, data packet synthesis module 120 aboard the bar code symbolreading device automatically produces a first (i.e., N=1) group of(three) data packets, each having the packet format shown in FIG. 9.Thereafter, the data packet transmission circuit 121 uses the digitaldata bit stream, representative of the synthesized data packet group, tomodulate a carrier signal transmitted from the hand-supportable bar codesymbol reading device.

[0175] In the illustrative example shown FIG. 10, only the second andthird data packets of the group sent over the modulated carrier signalare shown as being received by the preassigned base unit. As shown inthis drawing, the base unit transmits the recovered symbol characterdata D.sub.3 to its host computer system, upon receiving the second datapacket in the transmitted group of data packets. Thereafter, the baseunit produces an acoustical acknowledgement signal S.sub.ACK ofsufficient intensity that it can be easily heard by the operator of thebar code symbol reading device that transmitted the received datapacket. The function of the acoustical acknowledgment signal is toprovide the operator with an audible acknowledgement that the symbolcharacter data D.sub.3 (associated with the recently read bar codesymbol) has been received by the base unit and transmitted to its hostcomputer system for processing and or subsequent storage. Notably, whilethe third data packet N.sub.3 is also received by the base unit, theavailable acknowledgement signal S.sub.ACK and symbol character datatransmission is not produced as packet N.sub.3 contains redundantinformation already received by the second packet N.sub.2 of the samegroup.

[0176] In the preferred embodiment, the pitch of the transmittedacoustical acknowledgement signal S.sub.ACK is uniquely specified andassigned to a particular bar code symbol reading unit. This way theoperator of each bar code symbol reading (sub) system can easilyrecognize (i.e., discern) the audible acoustical acknowledgement signalproduced from the base unit preassigned to his or her bar code symbolreading device. At the same time, this pitch assigmnent scheme allowseach operator to ignore audible acoustical acknowledgment signalsproduced from neighboring base units not mated with his or her portablebar code symbol reading device. If after reading a bar code symbol, theoperator does not see the visual “good read” indication light on itsdevice “flash” or “blink” and immediately thereafter hear itspreassigned acoustical acknowledgement signal emanate from its baseunit, then the operator is implicitly informed that the symbol characterdata of the read bar code symbol was not successfully received by thebase unit. In response to such an event, the operator simply rereads thebar code symbol and awaits to hear the acoustical acknowledgment signalemanating from the base unit.

[0177] Notably, it may even be desirable in some operating environmentsto produce acoustical acknowledgement signals in the form of a uniqueseries of notes preassigned to a bar code symbol reading device and its“mated” base unit. The pitch or note sequence assigned to each matedbase unit and bar code symbol reading device can be stored in a memory(e.g., EPROM) realized in the base unit, and can be programmed at thetime of system set-up and modified as required. Preferably, each pitchand each note sequence is selected so that it can be readilydistinguished and recognized by the operator to which it is uniquelydirected.

[0178] Also shown in FIG. 10 is the case where the bar code symbolreading device reads a second bar code symbol and then transmits asecond (N=2) group of data packets. However, due to interference onlythe third data packet in the second transmitted group of data packets isreceived at the respective base unit. Despite such group transmissionerrors (e.g., due to channel corruption or non-radio transmissiveobstructions), the base unit as shown is nevertheless able to recoverthe transmitted symbol character data. Upon receiving the third datapacket, recovering the packaged symbol character data and transmittingthe same to the host computer system, the bar code symbol reading devicegenerates an acoustical acknowledgement signal having a pitch or notesequence that the operator can hear and recognize as an indication thatthe data packet reception was successful.

[0179] In FIGS. 11 and 12, the data packet transmission and receptionscheme of the present invention is shown for the case of three stationsystem. In the best case scenario shown in FIG. 11, the group of datapackets transmitted from each bar code symbol reading device istransmitted at a time when there are no neighboring bar code symbolreading devices transmitting data packets. This case will occur mostfrequently, as the total transmission times for each group of datapackets is selected to be substantially smaller than the random timedurations lapsing naturally between adjacent data packet transmissionsfrom neighboring bar code symbol reading devices. This fact isillustrated in FIG. 11, in which (i) a group of data packets from barcode reading device No. 1 are transmitted between adjacent groups ofdata packet transmitted from bar code symbol reading devices Nos. 2, 3and 4 without the occurrence of data packet interference (i.e.,collision). In most instances, the time delay between consecutive groupsof data packets transmitted from any particular bar code symbol readingdevice, will be sufficient to permit a neighboring bar code symbolreading device to transmit at least one data packet to its base unitwithout the occurrence of data packet interference.

[0180] In accordance with the data transmission scheme of the presentinvention, data packet interference is minimized by the random presenceof interference-free time slots, during which a transmitted data packetcan be received at its respective base unit without neighboring packetinterference. However, the present invention employs additional measuresto further reduce the likelihood of data packet interference. Suchmeasures are best appreciated when considering a high-density datapacket transmission environment, in which a number of closely situatedneighboring bar code symbol readers are each attempting to transmit agroup of data packets to its preassigned base unit. In general, suchoperating conditions would present a worst case scenario for, the datapacket transmission scheme of the present invention.

[0181] In the worst case scenario shown in FIG. 12, each of the fourneighboring bar code symbol reading devices is assumed to consecutivelyread two bar code symbols and simultaneously begin the transmission ofthe first data packet in the first group of data packets correspondingto the first read bar code symbol. As mentioned above, each data packetis formatted essentially the same way, has substantially the same packetwidth, and is transmitted on a carrier signal having a frequency whichis substantially the same as all other carrier signals transmittedthroughout the system. In accordance with the principles of the presentinvention, the data packet transmission circuit 121 in each bar codesymbol reading device is preprogrammed to transmit adjacent data packetswith a different “time delay”, as shown in FIG. 12. This condition isachieved throughout the resulting system by assigning a different PacketTime Delay to each having a different Transmitter Identification Number,and then programming the bar code symbol reading device with thepreassigned Packet Time Delay parameter. As illustrated in FIG. 12, thevalue of the Packet Time Delay parameter programmed in each bar codesymbol reading device is selected so that, when the neighboring bar codesymbol reading devices simultaneously transmit groups of data packets,each base unit in the resulting system is capable of receiving at leastone data packet (in a group thereof) that has been transmitted from itspreassigned bar code symbol reading device. In general, the data packetdelay scheme of the present invention involves selecting and programmingthe Packet Time Delay parameter in each bar code symbol reading deviceso that each base unit is periodically provided a vacant time slot,during which one transmitted data packet in each group thereof can bereceived free of “data packet interference”, as shown in FIG. 12. Theadvantage of providing a packet time delay among the data packets ofeach transmitted group thereof is that rereading and retransmission ofbar code symbols is effectively minimized under the data packettransmission scheme of the present invention.

[0182] Having described the detailed structure and internal functions ofautomatic bar code symbol reading device of the present invention, theoperation of the control system thereof will now be described whilereferring to the system block diagram shown in FIG. 8 and control BlocksA to GG in FIGS. 13A to 13C.

[0183] Beginning at the START block of Main System Control Routine andproceeding to Block A of FIG. 13A, the bar code symbol reading system is“initialized”. This initialization step involves, activating systemoverride circuit 100, first control circuit C.sub.1 and oscillatorcircuit 101. It also involves deactivating (i.e., disabling): (i) allexternal system components except the range selection circuit 115 andsystem override signal producing means 103 (i.e., infrared sensingcircuit 105, laser scanning circuit 108, and photoreceiving circuit109); (ii) all subcircuits aboard ASIC chip 133 not associated with thesystem override circuit 100, such as object detection circuit 107, A/Dconversion circuitry 110, second control circuit C.sub.2 and bar codepresence detection circuit 111; and (iii) third control module 114,symbol decoding module 119 and data packet synthesis module 120. Inaddition, all timers T.sub.1, T.sub.2, T.sub.3, T.sub.4, and T.sub.5 arereset to t=0.

[0184] Proceeding to Block B in FIG. 13A, the first control circuitC.sub.1 checks to determine whether it has received control activationsignal A.sub.0=1 from system override detection circuit 100. If thissignal is received, then the first control circuit C.sub.1 returns toBlock A. If control activation signal A.sub.0=1 is not received, then atBlock C the first control circuit C.sub.1 activates (i.e., enables) theobject detection circuit by producing E.sub.0. At Block D, the objectdetection circuit receives either the long range mode selection signalor the short range mode selection signal produced by the range selectioncircuit 115 and sets the appropriate sensitivity level of the circuit.At Block E, the first control circuit C.sub.1 determines whether it hasreceived control activation signal A.sub.1=1, indicating that an objecthas been detected within the selected range of the scan field. If thiscontrol activation signal is not received, then at Block F the firstcontrol circuit C.sub.1 determines whether its has received controlactivation signal A.sub.0=1. If the first control circuit C.sub.1 hasreceived control activation signal A.sub.0=1, then the control systemreturns to Block A in FIG. 13A, as shown. If the first control circuitC.sub.1 has not received control activation signal A.sub.0=1, then thecontrol system returns to Block E, as shown.

[0185] If at Block E the first control circuit C.sub.1 has receivedfirst control activation signal A.sub.1=1, then at Block G the firstcontrol circuit C.sub.1 (i) deactivates (i.e., disables) the objectsensing circuit and the object detection circuit using disabling signalE.sub.0=0, (ii) activates (i.e., enables) laser scanning circuit 108,photoreceiving circuit 109 and A/D signal conversion circuit 110 usingenable signal E.sub.1=1, (iii) activates bar code detection circuit 111and second control circuit C.sub.2 using enable signal E.sub.2=1, and(iv) starts timer T.sub.1 maintained in the first control circuitC.sub.1. This permits the bar code symbol reading device to collect andanalyze scan data signals for the purpose of determining whether or nota bar code is within the scan field. If at Block H the second controlcircuit C.sub.2 does not receive control activation signal A.sub.2S=1 orA.sub.2L=1 from the bar code detection circuit within time periodT.sub.1, indicating that a bar code symbol is detected in the selectedrange of the scan field, then the control system returns to Block Athereby returning system control to the first control unit C.sub.1, asshown in FIG. 13A. If at Block H the bar code symbol detection circuit111 provides the second control circuit C.sub.2 with control activationsignal A.sub.2S=1 or A.sub.2L=1, as the case may be, then second controlcircuit C.sub.2 activates (i.e., enables) third control module C.sub.3(i.e., microprocessor 134) using enable signal E.sub.3=1.

[0186] At Block J, the third control module C.sub.3 polls (i.e., reads)the parameter R set by range selection circuit 115 and sets a rangelimit flag in the symbol decoding module 119. At Block K third controlmodule C.sub.3 activates the symbol decoding module 119 using enablesignal E.sub.4, resets and restarts timer T.sub.2 permitting it to runfor a second predetermined time period (e.g., 0<T.sub.2<1 second), andresets and restarts timer T.sub.3 permitting it to run for a thirdpredetermined time period (e.g., 0<T.sub.3<5 seconds). At Block L thethird control module checks to determine whether control activationsignal A.sub.3=1 is received from the symbol decoding module 119 withinT.sub.2=1 second, indicative that a bar code symbol has beensuccessfully read (i.e., scanned and decoded) within the allotted timeperiod. If control activation signal A.sub.3=1 is not received withinthe time period T.sub.2=1 second, then at Block M third control moduleC.sub.3 checks to determine whether control activating signal A.sub.2=1is received. If a bar code symbol is not detected, then the controlsystem returns to Block A, causing a state transition from bar codereading to object detection. However, if at Block M the third controlmodule C.sub.3 receives control activation signal A.sub.2=1, indicativethat a bar code once again is within the scan field, then at Block N thethird control module C.sub.3 checks to determine whether time periodT.sub.3 has elapsed. If it has, then the control system returns to BlockA. If, however, time period O.ltoreq.T.sub.3.ltoreq.5 seconds has notelapsed, then at Block K the third control module C.sub.3 resets andrestarts timer T.sub.2 to run once again for a time periodO.ltoreq.T.sub.2.ltoreq.1 second, while T.sub.3 continues to run. Inessence, this provides the device at least another opportunity to read abar code present within the scan field when the control system is atcontrol Block L. During typical bar code reading applications, thecontrol system may progress through the control loop defined by BlocksK-L-M-N-K several times before a bar code symbol in the scan field isread within the time period allotted by timer T.sub.3.

[0187] Upon receiving control activation signal A.sub.3=1 from symboldecoding module 119, indicative that a bar code symbol has beensuccessfully read, the control system proceeds to Block O in FIG. 13B.At this stage of the system control process, the third, control moduleC.sub.3 continues activation of laser scanning circuit 108,photoreceiving circuit 109, and A/D conversion circuit 110, whiledeactivating symbol decoding module 119 and commencing activation ofdata packet synthesis module 120. While the laser beam is continuouslyscanned across the scan field, the operations at Blocks P to V describedbelow, are carried out in a high speed manner under the orchestration ofcontrol module C.sub.3.

[0188] As indicated at Block P, data packet synthesis module 120 firstsets the Packet Number to “1”, and increments the Packet Group Numberfrom the previous number. Preferably, the data packet synthesis modulekeeps track of (i.e., manages) the “Packet Number” using a firstmodulo-N counter realized by programmable microprocessor 134, while itmanages the “Packet Group Number” using a second modulo-M counter alsorealized by programmed microprocessor 134. In the illustrativeembodiment, the first modulo counter has a cyclical count range of N=2(i.e., 0, 1, 2, 0, 1, 2, . . . ), whereas the second modulo counter hasa cyclical count range of M=10 (i.e., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0,1, 2, . . . ). At Block Q, the data packet synthesis module synthesizesor constructs a data packet having a packet format as shown in FIG. 9,i.e., consisting of symbol character data, a Transmitter IdentificationNumber, a Packet Number, a Packet Group Number, check character, andPacket Start and End (i.e., framing) Characters. After the data packethas been formed and the digital data sequence constituting the same isbuffered, the third control module C.sub.3 activates at Block R the datapacket transmission circuit. Thereafter at Block S, the data packetsynthesis module outputs the buffered digital data sequence (of thefirst synthesized data packet of the group) to the data packettransmission circuit, which uses the digital data sequence to modulatethe frequency of the carrier signal as it is being transmitted from thebar code symbol reading device, to its mated base unit, as describedhereinabove, and then automatically deactivates itself to conservepower.

[0189] At Block T, the third control module C.sub.3 determines whetherthe Packet Number counted by the first module counter is less than “3”.If the Packet Number of the recently transmitted data packet is lessthan “3”, indicative that at most only two data packets in a specificgroup have been transmitted, then at Block U the data packet synthesismodule 120 increments the Packet Number by +1. At Block V, the thirdcontrol module then waits for a time delay T.sub.5 to lapse prior to thecontrol system returning to Block Q, as shown in FIG. 13B. Notably, theoccurrence of time delay T.sub.5 causes a delay in transmission of thenext data packet in the data packet group. As illustrated in FIG. 12,the duration of time delay T.sub.5 is a function of the (last two digitsof the) Transmitter Numbers of the current data packet group, and thusis a function of the bar code symbol reading device transmitting symbolcharacter data to its mated base unit. For the case of three data packetgroups, time delay T5 will occur between the transmission of the firstand second data packets in a packet group and between the transmissionof the second and third data packets in the same packet group.

[0190] Returning to Block Q, the data packet synthesis modulesynthesizes or constructs the second data packet in the same data packetgroup. After the second data packet has been formed and the digital datasequence constituting the same is buffered, the third control moduleC.sub.3 reactivates at Block R the data packet transmission circuit.Thereafter at Block S, the data packet synthesis module outputs thebuffered digital data sequence (of the second synthesized data packet)to the data packet transmission circuit, which uses the digital datasequence to modulate the frequency of the carrier signal as it is beingtransmitted from the bar code symbol reading device, to its mated baseunit, and thereafter automatically deactivates itself. When at Block Tthird control module C.sub.3 determines that the Packet Number is equalto “3”, the control system advances to Block W in FIG. 13C.

[0191] At Block W in FIG. 13C, the third control module C.sub.3continues activation of laser scanning circuit 108 photoreceivingcircuit 109, and A/D conversion circuit 110 using control overridesignals C.sub.3/C.sub.1, and deactivates symbol decoding module 119,data packet synthesis module 120 and the data packet transmissioncircuit 121 using disable signals E.sub.4=0, E.sub.5=0 and E.sub.6=0,respectively. Then at Block X the third control module C.sub.3determines whether control activation signal A.sub.1=1, indicating thatan object is present in the selected range of the scan field. If thiscontrol activation signal is not provided to the third control moduleC.sub.3 then the control system returns to Block A, as shown. If controlactivation signal A.sub.1=1 is received, then at Block Y the thirdcontrol module C.sub.3 reactivates the bar code symbol detection circuitusing override signal C.sub.3/C.sub.2, and resets and restarts timerT.sub.3 to start running over its predetermined time period, i.e.,0<T.sub.3<5 seconds, and resets and restart timer T.sub.4 for apredetermined time period 0<T.sub.4<3 seconds.

[0192] At Block Z in FIG. 13C, the third control module C.sub.3 thendetermines whether control activation signal A.sub.2=1 is produced fromthe bar code symbol detection circuit 111 within time period T.sub.4,indicating that a bar code symbol is present in the selected range ofthe scan field during this time period. If this signal is not producedwithin time period T.sub.4, then at Block AA the third control moduleC.sub.3 deactivates the bar code symbol detection circuit using overridesignal C.sub.3/C.sub.2, and reactivates the bar code symbol decodingmodule 119 using enable signal E.sub.4=1. At Block BB, the third controlmodule C.sub.3 resets and restarts timer T.sub.2 to run over itspredetermined time period, i.e., 0<T.sub.2<1 second. At Block CC thethird control module C.sub.3 determines whether control activationsignal A.sub.3=1 is produced by the symbol decoding module within timeperiod T.sub.2, indicating that the detected bar code symbol has beensuccessfully decoded within this time period. If this control activationsignal is not produced within time period T.sub.2, then at Block DD thethird control module C.sub.3 determines whether control activationsignal A.sub.2=1 is being produced from the bar code symbol detectioncircuit, indicating that either the same or another bar code symbolresides within the selected range of the scan field. If controlactivation signal A.sub.2=1 is not being produced, then the controlsystem returns to Block A, as shown. However, if this control signal isbeing produced, then at Block EE the third control module C.sub.3determines whether or not timer T.sub.3 has lapsed, indicating that timewindow to read a bar code symbol without redetecting the object on whichit is disposed, is closed. When this condition exists, the controlsystem returns to Block BB FIG. 13A. However, it time remains on timerT.sub.3, then at Block A in the third control module C.sub.3 resets andrestarts timer T.sub.2 and returns to Block CC. As mentioned above, thecontrol system may flow through the control loop defined by BlocksBB-CC-DD-EE-BB a number of times prior to reading a bar code within timeperiod T.sub.3.

[0193] When the symbol decoding module produces control activationsignal A.sub.3=1 within time period T.sub.2, the third control moduleC.sub.3 determines at Block FF whether the decoded bar code symbol isdifferent from the previously decoded bar code symbol. If the decodedbar code symbol is different than the previously decoded bar codesymbol, then the control system returns to Block 0 in FIG. 13B. If thecurrently decoded bar code symbol is not different than the previouslydecoded bar code symbol, then the third control module C.sub.3determines whether timer T.sub.3 has lapsed. If the timer T.sub.3 hasnot lapsed, then the control system returns to Block BB and reenters thecontrol flow defined at Blocks BB through GG, attempting once again todetect and read a bar code symbol on the detected object. However, if atBlock GG timer T.sub.3 has lapsed, then the control system returns toBlock A in FIG. 13A.

[0194] Having described the operation of the illustrative embodiment ofthe automatic hand-supportable bar code reading device of the presentinvention, it will be helpful to describe at this juncture the variousconditions which cause state transitions to occur during its operation.In this regard, reference is made to FIG. 14 which provides a statetransition diagram for the it illustrative embodiment.

[0195] As illustrated in FIG. 14, the automatic hand-supportable barcode reading device of the present invention has four basic states ofoperation namely: object detection, bar code symbol presence detection,bar code symbol reading, and symbol character data transmission/storage.The nature of each of these states has been described above in greatdetail.

[0196] Transitions between the various states are indicated bydirectional arrows. Besides each set of directional arrows aretransition conditions expressed in terms of control activation 11signals (e.g., A.sub.1, A.sub.2S or A.sub.2L and A.sub.3, and whereappropriate, state time intervals (e.g., T.sub.1, T.sub.2, T.sub.3,T.sub.4, and T.sub.5) Conveniently, the state diagram of FIG. 14expresses most simply the four basic operations occurring during thecontrol flow within the system control program of FIGS. 13A to 13C.Significantly, the control activation signals A.sub.1, A.sub.2S A.sub.2Land A.sub.3 in FIG. 14 indicate which events within the object detectionand/or scan fields can operate to effect a state transition within theallotted time frame(s), where prescribed.

[0197] Referring now to FIGS. 15 to 15C, the base unit of theillustrative embodiment of the present invention will be described ingreater detail.

[0198] In order to perform the data packet reception, processing,retransmission, and acknowledgement functions of base unit 3 describedabove, a circuit board 270 is mounted within the interior volume ofsupport stand portion 14. In the illustrated embodiment, PC board 270 ispopulated with electronic circuitry and devices for realizing each ofthe functions represented by the block shown in the system diagram ofFIG. 16. As shown in FIG. 15A, flexible communication and power supplycables 7 and 8 are routed through aperture 271 formed in the lowerportion of side wall of the support frame, and connect to the electroniccircuitry on PC board 270.

[0199] In FIG. 16, the system architecture of base unit 3 isschematically represented. As shown, base unit 3 comprises a numberhardware and software components, namely: a power supply circuit 273; areceiving antenna element 274; an RF carrier signal receiver circuit 275base unit identification number storage unit 276; a data packet storagebuffer 277; a base unit system controller 278; a data packet frame checkmodule 279; a transmitter number identification module 280; a datapacket number identification module 281; a symbol character dataextractions module 282; a data format conversion module 283; a serialdata transmission circuit 284; and an acoustical acknowledgement signalgeneration circuit 285. In the illustrative embodiment, a programmedmicroprocessor and associated memory (i.e., ROM and RAM), indicated byreference numeral 286, are used to realize the base unit systemcontroller 278 and each of the above-described data processing modules277 to 283. The details of such a programming implementation are knownby those with ordinary skill in the art to which the present inventionpertains.

[0200] As shown in FIG. 16, receiving antenna element 274 iselectrically coupled to an input signal port of radio receiver circuit275 in a conventional manner. In general, the function of radio receivercircuit 275 is to receive and process the data-packet modulated carriersignal transmitted from a remote bar code symbol reader to its matedbase unit. The radio receiver circuit of the illustrative embodiment canbe realized by configuring several commercially available IC chipstogether, although it is understood that there are certainly other waysin which to realize the basic functions of this circuit. As shown inFIG. 16A, receiving antenna 274 is connected to a matching filtercircuit 287 realized using miniature inductive and capacitivecomponents. The matching filter circuit is tuned to pass a 912 MHz RFcarrier signal transmitted from the data packet transmission circuit 121of the bar code symbol reading device. The output of matching filtercircuit 287 is connected to the input of a first IC chip 288 whichconverts (i.e., translates) the frequency spectrum of the receivedmodulated carrier signal down to an intermediate frequency band, forsubsequent signal processing. In the illustrative embodiment, the firstIC chip 288 is realized using the MAF2001 IC chip from Motorola, Inc.,and provides a low noise amplifier 289, an double balanced mixer 290. Alocal oscillator 292 is needed to provide a local oscillator signal ofabout 922.7 MHZ for use in frequency down-conversion in the doublebalanced mixer 290. Typically, a matching filter 291 is commonlyrequired between local oscillator 292 and mixer 290. As shown in FIG.16A, the output of the first IC chip is provided to a band-pass filter293 tuned to about 10.7 MHZ, the intermediate frequency band of eachbase unit. The intermediate signal is then provided as input to a secondIC chip 294. In the illustrative embodiment, the second IC chip 294 isrealized using the MC13156 IC chip commercially available from Motorola,and provides inter alia an amplification circuit, a quadraturedemodulation circuit 295, a binary thresholding circuit 296, and carriersignal detection circuit 297. The function of the second IC chip isfour-fold. The first function of the second IC chip is to filter andamplify the intermediate signal to produce in-phase and quadrature phasesignal components for use in digital data recovery. The second functionof the second IC chip is to recover an analog data signal at the baseband portion of the spectrum, by providing the in-phase andquadrature-phase signal components to the quadrature demodulationcircuit 295. Suitable quadrature demodulation circuitry for use inpracticing the present invention is disclosed in U.S. Pat. No. 4,979,230to Marz, which is incorporated herein by reference in its entirety. Asillustrated in FIG. 16A, the third function of the second IC chip is toconvert the analog data signal produced from quadrature demodulationcircuit 295 into a digital data signal using a binary-level thresholdingcircuit 296. The fourth function of the second IC chip is to analyze theincoming signal from the output of band-pass filter 293 in order todetect the incoming carrier signal and produce a carrier detect signalA.sub.7 to the base unit system controller 278. In order to produce aCMOS compatible signal, the recovered digital data signal produced fromsecond IC chip 294 is amplified by a current amplification circuit 298that is operative whenever a carrier signal is detected (i.e.,A.sub.7=1). As shown in FIG. 16, the output of current amplification,circuit 298 is a serial data stream that is clocked into data packetstorage buffer 277 under the control of base unit system controller 278.In general, the data packet storage buffer 277 can be realized using acommercially available Universal Asynchronous Receiver/Transmitter(UART) device. The primary function of data packet buffer memory 277 isto buffer bytes of digital data in the produced digital data stream.

[0201] In the illustrative embodiment, it necessary to provide a meanswithin the base unit housing, to recharge the batteries contained withinthe hand-supportable housing of the portable bar code symbol readingdevice. Typically, DC electrical power will be available from the hostcomputer system 6, to which, the base unit is operably connected by wayof flexible cables 7 and 8. An electrical arrangement for achieving thisfunction is set forth in FIG. 16. As shown, power supply circuit 273aboard the base unit of the present invention comprises a conventionalcurrent chopper circuit 299, a high-pass electrical filter 300 inparallel therewith, and a primary inductive coil 301 in parallel withthe high-pass electrical filter. Low voltage DC electrical powerprovided from the host computer system by way of power cable 8 isprovided to direct current (DC) chopper circuit 299, which is realizedon PC board 270 using high-speed current switching circuits. Thefunction of current chopper circuit 299 is to convert the input DCvoltage to the circuit into a high-frequency triangular-type(time-varying) waveform, consisting of varilous harmonic signalcomponents. The function of the high-pass electrical filter is to filterout the lower frequency signal components and only pass the higherfrequency signal components to the inductive coil 301. As such, the highfrequency electrical currents permitted to flow through inductive coil301 induce a high voltage thereacross and produce time-varying magneticflux (i.e., lines of force). In accordance with well known principles ofelectrical energy transfer, the produced magnetic flux transferselectrical power from the base unit to the rechargeable battery aboardthe bar code symbol reading device, whenever the primary and secondaryinductive coils aboard the base unit and the mated device areelectromagnetically coupled by the magnetic flux. In order to maximizeenergy transfer between the base unit and its mated device duringbattery recharging operations, high permeability materials and wellknown principles of magnetic circuit design can be used, to increase theamount of magnetic flux coupling the primary and secondary inductivecoils of the battery recharging circuit.

[0202] Referring to FIG. 16, the function of each of the data processingmodules of base unit 3 will now be described in detail.

[0203] Upon reception of an incoming carrier signal and the recovery ofthe digital data stream therefrom, base unit system controller 278orchestrates the processing of the recovered digital data stream. Asshown in FIG. 16, the operation of data processing modules 279, 280,281, 282 and 283 are enabled by the production of enable signalsE.sub.PFC, E.sub.TID, E.sub.DPID, E.sub.DE, and E.sub.DFC, respectively,from the base unit system controller.

[0204] The primary function of data packet frame check module 279 is toanalyze all of the data bytes in the received data packet, including theStart and End of Packet Fields, and determine whether a complete frame(i.e., packet) of digital data bytes has been recovered from theincoming modulated carrier signal. If so, then data packet frame checkmodule 279 produces activation control signal A.sub.PFC=1, which isprovided to the base unit system controller, as shown in FIG. 16.

[0205] The primary function of the transmitter number identificationmodule 280 is to analyze the data bytes in the Transmitter ID Field ofthe received data packet and determine the Transmitter ID Numberpreassigned to the bar code reading device that transmitted the datapacket received by the base unit. If the Transmitter ID Number of thereceived data packet matches the preassigned Base Unit IdentificationNo. stored in non-volatile memory (i.e., EPROM) 302 aboard the baseunit, then the transmitter number identification module generatescontrol activation signal A.sub.TID=1, which is provided to the baseunit system controller.

[0206] The primary function of the packet number identification module281 is to analyze the data bytes in the Packet Number Field of thereceived data packet and determine the Packet Number of the data packetreceived by the base unit. This module then advises the base unit systemcontroller that, a different packet number was received, representing anew group (e.g., now seen) by producing an encoded signal A.sub.DPIDduring the system control process.

[0207] The primary function of the symbol character data extractionmodule 282 is to analyze the data bytes in the Symbol Character DataField of the received data packet, determine the code represented by thesymbol character data, and provided this symbol character data to thedata format conversion module 283 under the control of the base unitsystem controller during the system control process.

[0208] The primary function of the data format conversion module 283 isto convert the format of the recovered symbol character data, into adata format that can be used by the Lost computer symbol 6 that is toultimately receive and use the symbol character data. In the bar codesymbol reading system of first illustrative embodiment, the data formatconversion is from ASCII format to RS232 format, although it isunderstood that other inversions may occur in alternative embodiment ofthe present if invention. Typically, the data format conversion processis carried out using a data format conversion table which contains theappropriate data structure conversions.

[0209] The primary function of the serial data transmission circuit 284is to accept the format-converted symbol character data from the dataformat conversion module 283, and transmit the same :1 as a serial datastream over data communication cable 7, to the data input port of thehost computer system 6 (e.g., cash register, data collection device,inventory computer). Preferably, an RS-232 data communication protocolis used to facilitate the data transfer process. Thus the constructionof serial data transmission circuit 284 is conventional and the detailsthereof are well within the knowledge of those with ordinary skill inthe art.

[0210] The primary function of acoustical acknowledgement signalgeneration circuit 285 is to produce an acoustical acknowledgementsignal SA in response to the successful recovery of symbol characterdata from a transmitted data packet. The purpose of the acousticalacknowledgement signal is to notify the user that the transmitted datapacket has been successfully received by its mated base unit. In theillustrative embodiment, the intensity of the acoustical acknowledgementsignal is such that the remotely situated user of the portable bar codesymbol reader can easily hear the acoustical acknowledgement signal inan expected work environment having an average noise floor of at leastabout 50 decibels. Preferably, the pitch of the acousticalacknowledgement signal is within the range of about 1 to about 10kilohertz, in order to exploit the sensitivity characteristics of thehuman auditory apparatus of the user. In the exemplary embodiment, thepitch is about 2.5 kilohertz. Under such conditions, the intensity ofsuch an acoustical acknowledgement signal at its point of generationwill typically need to have an output signal power of about 70 decibelsin order to be heard by the user in a working environment having anaverage noise floor of about 50 decibels and an average noise ceiling ofabout 100 decibels. Acoustical acknowledgement signals of such charactercan be produced from acoustical acknowledgement signal generationcircuit 285, shown in FIG. 16.

[0211] As shown in FIG. 16B, acoustical acknowledgement signalgeneration circuit 285 comprises a number of subcomponents, namely: adecoder circuit 305; a voltage controlled oscillator (VCO) drivercircuit 306; a VCO circuit 307; an output amplifier circuit 308; and apiezo-electric type electro-acoustic transducer 303 having an outputsignal bandwidth in the audible range. The operation (i.e., duration) ofthe acoustical acknowledgment signal generation circuit 285 iscontrolled by base unit system controller 278 using enable signalE.sub.AA. In the illustrative embodiment, enable signal E.sub.AA is adigital word encoded to represent one of a number of possible audiblepitches or tones that are to be generated upon each successful receptionof a transmitted data packet at a mated base station. The function ofdecoder circuit 305 is to decode the enable signal EAA produced by thebase unit system controller and produce a set of voltage signals{V.sub.1 1, V2, . . . , Vn} which correspond to a specified pitchsequence to be produced by eleclro-acoustic transducer 309. The functionof VCO driver circuit 306 is to sequentially drive VCO circuit 307 withthe produced set of voltages {V.sub.1 1, V2, . . . , Vn} so that VCOcircuit produces over a short time period (e.g., 0.5-1.5 seconds), a setof electrical signals having frequencies that correspond to thespecified pitch sequence to be produced from the electro-acoustictransducer 309. The function of amplifier circuit 308 is to amplifythese electrical, signals, whereas the function of electro-acousticaltransducer 309 is to convert the amplified electrical signal set intothe specified pitch sequence for the user to clearly hear in theexpected operating environment. As shown in FIGS. 1 and 15A, the basehousing is preferably provided with an aperture or sound port 304 so asto permit the energy of the acoustical signal from transducer 309 tofreely emanate to the ambient environment of the user. In particularapplication, it may be desired or necessary to produce acousticalacknowledgement signal of yet greater intensity levels that thosespecified above. In such instances, electro-acoustical transducer 309may be used to excite one or more tuned resonant chamber(s) mountedwithin or formed as part of the base unit housing.

[0212] Having described the structure and general functional componentsof base unit 3, it is appropriate at this juncture to now describe theoverall operation thereof with reference to the control process shown inFIG. 17.

[0213] As illustrated at Block A in FIG. 17, radio receiving circuit 275is the only system component that is normally active at this stage ofthe base unit system control process. All other system components areinactive (i.e., disabled), including base unit system controller 278;data packet storage buffer 277, data packet frame check module 279,transmitter number identification module 280, data packet numberIdentification module 281, symbol character data extraction module 282,data format conversion module 283, serial data transmission circuit 284,and acoustical acknowledgement signal generation circuit 285. With theradio receiving circuit activated, the base unit is capable of receivingany modulated carrier signal transmitted from any of the bar code symbolreading devices within the data transmission range of the base unit.

[0214] At Block B in FIG. 17, radio receiving circuit 275 deter-mineswhether it has received a transmitted carrier signal on its receivingantenna element 274. If it has, then the radio, receiving circuitgenerates a system controller activation signal A.sub.7, which activatesbase unit system controller 278 and signal amplifier 276 shown in FIGS.16 and 16A, respectively. Then at Block C, the base unit systemcontroller activates (i.e., enables) data packet storage buffer 277 anddata packet frame check module 279 by producing activation controlsignals ESB=1 and E.sub.PFC=1, respectively. At Block D, the base unitsystem controller determines whether it has received an acknowledgement(i.e., control activation signal A.sub.PFC=1) from the data packet framecheck module, indicating that the received data packet is properlyframed. If the received data packet is not properly framed, then thebase unit returns to Block A in order to redetect an incoming carriersignal. However, if the received data packet is properly framed, then atBlock E the base unit system controller enables the transmitter numberidentification module by generating enable signal E.sub.TID=1.

[0215] At Block F, the base unit system controller determines whether ithas received an acknowledgment (i.e., control activation signalA.sub.TID=1) from the transmitter number identification module that thereceived data packet contains the correct transmitter identificationnumber (i.e., the same number assigned to the base unit and stored instorage unit 276). If the Transmitter Identification Number containedwithin the received data packet does not match the base unitidentification number stored in storage unit 276, then the base unitsystem controller returns to Block A whereupon it resumes carrier signaldetection. If, however, the transmitter packet number contained withinthe received data packet matches the base unit identification number,then at Block G the base unit system controller enables the data packetnumber identification module 289 by generating enable signalE.sub.DPID=1.

[0216] At Block H, the base unit system controller determines whether ithas received an acknowledgment (i.e., control activation signalA.sub.PDID=1) from the data packet identification module indicating thatthe received data packet is not a redundant data packet (i.e., from thesame transmitted data packet group). If the received data packet is aredundant data packet, then the base unit system controller returns toBlock A, whereupon carrier signal detection; is resumed. If, however,the received data packet is not redundant, then at Block the base unitsystem controller enables the symbol character data extraction module bygenerating enable signal E.sub.DE=1. In response to the generation ofthis enable signal, the symbol data extraction module reads at Block Jthe symbol character data contained in the received data packet, checksthe data for statistical reliability, and the writes the extractedsymbol character data bytes into a storage buffer (not explicitlyshown).

[0217] As indicated at Block K in FIG. 17, the base unit systemcontroller then enables the data format conversion module by generatingenable signal E.sub.DFC=1. In response to this enable signal, the dataformat conversion module converts the data format of the recoveredsymbol character data and then buffers the format-converted symbolcharacter data bytes in a data buffer (not explicitly shown). At Block Lthe base unit system controller enables the serial data transmissioncircuit 284 by generating enable signal E.sub.DT=1. In response to thisenable signal, the serial data transmission circuit transmits theformat-converted symbol character data bytes over communication cable 7using serial data transmission techniques well known in the art, asdiscussed above. When the serial data transmission process issuccessfully completed, the base unit system controller enables at BlockM the acoustical acknowledgement signal generation circuit 285 byproducing enable signal E.sub.AA=1. In response to the production ofthis enable signal, acoustical acknowledgment signal generation circuit285 generates a high intensity acoustical signal having characteristicsof the type described above, thereby informing the user that atransmitted data packet has been received and that the symbol characterdata packaged therein has been successfully recovered and transmitted tothe host computer system. Thereafter, the base unit system controllerreturns to the Block A, as shown.

[0218] It is appropriate at this juncture to illustrate the automatichands-on and hands-free modes of operation of the system while utilizedin different mounting installations.

[0219] A point-of-sale station is shown in FIGS. 18A and 18B, ascomprising an electronic cash register 6 operably connected to theautomatic bar code reading system of the first illustrative embodimentby way of flexible communication cable 7. Low voltage DC power isprovided to base unit 3 by way of flexible power supply cable 8. In thisparticular mounting installation, base unit 3 is supported on ahorizontal countertop surface. If necessary or desired in such mountinginstallations, the base plate of base unit 3 may be weighted by affixingone or more dense mass elements to the upper surface of the base plate.

[0220] With automatic bar code reading device 2 supported within scannersupport stand portion of the base unit, the system is automaticallyinduced into its automatic long-range hands-free mode of operation. Thepositioning of both object detection and scan fields in this mountinginstallation allows bar code symbols on objects to be easily read. Inorder to induce the system into its short-range hands-on mode ofoperation, the user simply encircles the handle portion of thehand-supportable device with his or her fingers, and then lifts thedevice out of the scanner support stand. Upon lifting the device out ofits stand, the range selection circuit 115 (e.g., including aHalt-effectmagnetic flux sensor (mounted in the handle of the housing)detects the absence of magnetic flux produced from a permanent magnetmounted in the support stand, and automatically generates theshort-range control activation signal (i.e., R.sub.1=0). The details ofthis range mode-selection mechanism can be found in copendingapplication Ser. No. 07/761,123, now U.S. Pat. No. 5,340,971 supra.

[0221] With the automatic bar code reading device held in the user'shand, and a bar coded object 435 in the other hand, the object is movedinto the short-range portion of the object detection field as shown inFIG. 18B, where the object is automatically detected, and bar codesymbol 436 automatically scanned while the visible laser beam isrepeatedly scanned within the scanning volume. After the bar code symbolhas beer successfully read (i.e., detected and decoded) and atransmitted data packet containing symbol character data has beenreceived and processed at base unit 3 in a manner described hereinabove,a highly audible acoustical acknowledgement signal Sack of apredetermined pitch is produced from the base unit. Thereafter, the barcode reading device is placed back within the scanner support stand,where it is once again induced into its long-range hands-free mode ofoperation.

[0222] Having described the preferred embodiments of the presentinvention, several modifications come to mind.

[0223] In the system control process of the illustrative embodiment,shown in FIG. 8, the polygon 36 is actively driven to its desiredangular velocity only when the system is in its bar code symboldetection and read modes. In the illustrative embodiment, the moment ofinertia of the polygon 36 is ultra-low so that it can instantly attainits desired angular velocity (from rest) in a very short time from whenan object is detected within the 3-D scanning volume.

[0224] In an alternative embodiment of the present invention, thecontrol system of the laser scanner hereof can be modified so that thescanning polygon 36 is actively driven to idle at angular velocityW.sub.OD when the system is in its object detection mode, and activelydriven to its desired angular velocity W.sub.BCD (i.e., where W.sub.BCDW.sub.OD) when the system is in the bar code detection mode. Using thiscontrol process, the scanning polygon is permitted to quickly attain itsdesired operating velocity W.sub.BCD when an object is detected in thescanning volume, for subsequent scan data collection operations. Thiscontrol technique offers the advantage of using a polygon of a highmoment of inertia, with the option of periodically imparting torque tothe polygon motor shaft during the object detection state to maintainthe idling velocity W.sub.ODS in an electrically conservative manner.The motor control circuit hereof can be readily modified to realize sucha pulsed-torque functionality in the system of the present invention.

[0225] In an alternative embodiment, where power consumption is not ofcritical concern, the scanning polygon can be continuously driven to thedesired operating velocity at each state of system operation.

[0226] The automatic bar code reading system of the present invention iscapable of performing a wide variety of complex decision-makingoperations in real-time, endowing the system with a level ofintelligence hitherto unattained in the bar code symbol reading art.Within the spirit of the present invention, additional decision-makingoperations may be provided to further enhance the capabilities of thesystem.

[0227] While the various embodiments of the projection laser scannerhereof have been described in connection with linear (1-D) code symbolscanning applications, it should be clear, however, that the projectionlaser scanner of the present invention is suitable for scanning 2-D codesymbols as well as alphanumeric characters (e.g. textual information) inoptical character recognition (OCR) applications.

[0228] While the particular illustrative embodiments shown and describedabove will be useful in many applications in code symbol reading,further modifications to the present invention herein disclosed willoccur to persons with ordinary skill in the art. All such modificationsare deemed to be within the scope and spirit of the present inventiondefined by the appended claims to Invention.

What is claimed is:
 1. An optical scanner comprising: (a) a housinghaving an optically admissive window through which optical energy of atleast one wavelength can exit said housing, travel towards an objectbearing a code symbol and reflect therefrom, at least a portion of thereflected optical energy travelling back through the optically admissivewindow to enter the housing; wherein the housing has a central referenceaxis extending approximately upwards and downwards in a longitudinaldirection; (b) an optical energy producing mechanism disposed within thehousing for producing a beam of optical energy; (c) a beam sweepingmechanism mounted within the housing with respect to the centralreference axis for rotation about a rotational axis intersecting thecentral reference axis, where the intersection of the rotational axisand the central reference axis defines a central reference plane; thebeam sweeping mechanism including a plurality of rotating lightreflective surfaces each being disposed at a different acute angle withrespect to the rotational axis, for sequentially sweeping the beam aboutthe rotational axis along a plurality of different paths; (d) astationary array including a plurality of stationary opticallyreflective surfaces mounted within the housing with respect to thecentral reference axis and disposed substantially underneath saidoptically admissive window; wherein at least two of the plurality ofsaid stationary optically reflective surfaces are substantiallysymmetrically disposed on opposite sides of the central reference plane,and closely adjacent to the beam sweeping mechanism; (e) an opticalenergy collection subsystem disposed within the housing, and including(1) an optical collection element, mounted along the central referenceplane and adjacent at least two of the stationary optically reflectivesurfaces, for allowing the beam produced by the optical energy producingmechanism to pass along a portion of the central reference plane, to thebeam sweeping mechanism, for sweeping about the rotational axis thereofalong the plurality of different paths, and (2) an optical receiver forreceiving optical energy from the optical collection element at a pointsubstantially within the central reference plane, detecting the receivedoptical energy and producing an electrical signal indicative of saiddetected optical energy; (f) a signal processor for processing theelectrical signal and producing scan data representative of a scannedcode symbol; (g) a control mechanism for controlling the operation ofthe scanner so that, during scanner operation, the beam produced by theoptical energy producing mechanism passes along a portion of the centralreference plane, to at least one of the rotating optically reflectivesurfaces of the beam sweeping mechanism, and as the beam sequentiallyreflects off a plurality of the rotating light reflective surfaces, thebeam is repeatedly swept across a plurality of the stationary lightreflective surfaces, thereby producing a plurality of groups of pluralscan lines, respectively, which are projected out through the opticallyadmissive window and intersect about a projection axis within acollimated scanning volume having an approximately columnar extent andextending from adjacent the optically admissive window to at least aboutsix inches therefrom so as to produce a collimated projected scanningpattern; and (h) the housing being supportable relative to an objectbearing a code symbol so that when a code symbol is presented within thecollimated scanning volume, (i) the code symbol is scannedomnidirectionally by the collimated scanning pattern, (ii) at least aportion of the optical energy reflected from the scanned code symbol isdirected through the optically admissive window, reflected off at leastone of the stationary optically reflective surfaces, and then reflectedoff at least one of the rotating optically reflective surfaces of thebeam sweeping mechanism, and (iii) thereafter, the reflected opticalenergy is collected by the optical collection element, and received bythe optical receiver for detection, whereupon the electrical signal isproduced for processing by the signal processor; wherein the housingpermits a user to control the direction of the projection axis so as toalign the collimated scanning volume with the bar code symbol on theobject to be scanned.
 2. The scanner of claim 1 , wherein the signalprocessor further comprises a data processor for decoding the scan dataand producing data representative of the scanned code symbol.
 3. Thescanner of claim 1 , wherein said different acute angles are selected sothat the scan lines in each said group of scan lines are substantiallyequidistant from each other throughout at least a range of distancesfrom the optically admissive window.
 4. The scanner of claim 1 , whereinthe optical energy producing mechanism comprises a laser diode mountedwith respect to the central reference axis.
 5. The scanner of claim 1 ,wherein said first, second, third, and fourth stationary lightreflective surfaces comprise first, second, third, and fourth mirrors,respectively.
 6. The scanner of claim 1 , wherein the housing includes ahead portion and handle portion extending from the head portion, and theoptically admissive window is disposed within the head portion.
 7. Thescanner of claim 1 , wherein the collimated scanning pattern is orientedalong a longitudinal extent of the housing so as to facilitate scanningof code symbols presented to the collimated scanning volume.
 8. Thescanner of claim 1 , further comprising a scanner support standpositionable upon a counter surface, and including a supportingmechanism for supporting the housing in any one of a plurality ofpositions above a counter surface so that the collimated scanningpattern is projected about the projection axis above the counter surfacein any one of a plurality of orientations corresponding to the pluralityof positions.
 9. The scanner of claim 1 , further comprising an opticalbench mounted along the central reference axis, wherein the opticalbench includes a shock-mounted support structure upon which thestationary optically reflective surfaces are mounted.
 10. The scanner ofclaim 1 , wherein the optical receiver comprises a photodetector. 11.The scanner of claim 10 , wherein the photodetector is located on acircuit board, at a height above the beam sweeping mechanism,substantially within the central reference plane.
 12. The scanner ofclaim 1 , wherein said code symbol is a bar code symbol.
 13. The scannerof claim 1 , wherein the optical collecting element is a lightcollecting mirror having a focal distance, substantially at which saidoptical receiver is located.
 14. The scanner of claim 1 , wherein eachscan line in a first group of scan lines is substantially parallel toeach other scan line in said first group of scan lines, and each scanline in a second group of scan lines is substantially parallel to eachother scan line in said second group of scan lines.
 15. An automaticoptical scanning system comprising: a housing having an opticallyadmissive aperture through which optical energy of at least onewavelength can exit and enter into the housing; an object detector inthe housing, for detecting an object located in a scanning volumeextending externally from the housing, and automatically generating anactivation signal in response to the detection of the object locatedtherein; an activatable scan data reading mechanism in the housing, forreading scan data from a detected object located in the scanning volume,the scan data reading mechanism including: an optical beam generator forgenerating a beam of optical energy and directing the beam through theoptically admissive aperture and into the scanning volume, a beamscanner for repeatedly scanning the beam so as to produce a collimatedscanning pattern of approximately columnar extent within the scanningvolume, for scanning a code symbol on the detected object presentedtherein, an optical detector for detecting optical energy reflected offthe bar code symbol and passing through the optically admissive apertureas the beam is repeatedly scanned within the scanning volume, and areceiver for automatically producing scan data indicative of thedetected optical energy; an activatable scan data processor forprocessing produced scan data so as to detect and decode said bar codesymbol on the detected object, and automatically producing symbolcharacter data representative of the decoded bar code symbol; and acontrol mechanism for controlling the operation of the automatic barcode symbol reading system; wherein the housing permits the user tocontrol the direction of the projection axis to align said approximatelycolumnar scanning volume with the bar code symbol on the object to bescanned.
 16. The scanning system of claim 15 , wherein the optical beamgenerator comprises a laser diode.
 17. The scanning system of claim 15 ,wherein the bar code symbol has first and second envelope borders, andwherein said scan data processor comprises a detector adapted to detectthe first and second envelope borders of said bar code symbol, and amechanism for decoding said detected bar code symbol.
 18. The scanningsystem of claim 15 , wherein the object detector comprises a receiverfor receiving optical energy reflected from an object within an objectdetection field defined external to the housing and having anessentially volumetric extent, and wherein the collimated scanningpattern is characterized by at least one scanning plane having anessentially planar extent, and wherein the object detection fieldspatially encompasses at least a portion of the collimated scanningpattern.
 19. The laser scanning system of claim 15 , wherein the opticalbeam generator is operated in a pulsed mode so as to generate a pulsedbeam, which is directed through the optically admissive aperture andrepeatedly scanned across the collimated scanning pattern and the barcode symbol on the detected object.
 20. The scanning system of claim 19, wherein the object detector includes a transmitter for transmitting apulsed signal through a first optical element and into the scanningvolume, a signal receiver for receiving the transmitted pulse signalreflected off the object in the scanning volume, and a signal comparatorfor comparing the received pulse signal with the transmitted pulsesignal and automatically generating an activation signal indicative ofthe presence of the object in the scanning volume.
 21. The scanningsystem of claim 15 , wherein the housing comprises a head portion and ahandle portion, and wherein the object detector and the activatable scandata processor are located in the head portion.
 22. The scanning systemof claim 20 , wherein the transmitter comprises an infra-red lightsource in the housing for producing an infra-red light pulse which istransmitted through the first optical element into the scanning volume,and wherein the receiver comprises an infra-red light detector and asecond optical element for focusing reflected infra-red light pulsesonto the infrared light detector.
 23. A scanner comprising: (a) ahousing having an optically admissive window through which opticalenergy of at least one wavelength can exit said hand-supportablehousing, travel towards an object bearing a code symbol and reflecttherefrom, and at least a portion of the reflected optical energytravelling back through the optically admissive window to enter thehousing; at least some of the exited optical energy and at least some ofthe reflected optical energy traveling approximately in a longitudinaldirection extending along a central reference axis; (b) an opticalenergy beam producing mechanism disposed within the housing forproducing a beam of optical energy; (c) a beam sweeping mechanismmounted within the housing for rotation about a rotational axisintersecting the central reference axis, where the intersection of therotational axis and the central reference axis defines a centralreference plane; the beam sweeping mechanism having a plurality ofrotating optically reflective surfaces each being disposed at adifferent acute angle with respect to the rotational axis, forsequentially sweeping the beam about the rotational axis along aplurality of different paths; (d) a stationary array comprised of aplurality of stationary optically reflective surfaces mounted within thehousing; wherein at least two of the plurality of the stationaryoptically reflective surfaces are symmetrically disposed on oppositesides of the central reference plane, and adjacent to the beam sweepingmechanism; (e) an optical energy collection mechanism disposed withinthe housing, and including (1) an optical collection element, mountedalong the central reference plane and adjacent at least two of thestationary optically reflective surfaces, for allowing the beam producedfrom the beam producing mechanism to pass along a portion of the centralreference plane, to the beam sweeping mechanism, for sweeping about therotational axis thereof along the plurality of different paths, and (2)an optical receiver for receiving optical energy from the opticalcollection element at a point substantially within the central referenceplane, and detecting the received optical energy and producing anelectrical signal indicative of the detected optical energy; (f) asignal processor for processing the electrical signal and producing scandata representative of a scanned code symbol; and (g) a controlmechanism for controlling the operation of the scanner so that, duringscanner operation, the beam produced from the beam producing mechanismpasses along a portion of the central reference plane, to at least oneof the rotating light reflective surfaces of the beam sweepingmechanism, and as the beam sequentially reflects off a plurality of therotating optically reflective surfaces, the beam is repeatedly sweptacross a plurality of the stationary optically reflective surfacesthereby producing a plurality of groups of plural scan lines,respectively, which are projected out through the optically admissivewindow and intersect about a projection axis within a collimatedscanning volume having an approximately columnar extent and extendingfrom adjacent said optically admissive window to at least about sixinches therefrom so as to produce a collimated projected scanningpattern.
 24. The scanner of claim 23 further comprising a mechanismadapted for intuitive aiming of the housing such that: (i) the housingis supportable relative to an object bearing a code symbol wherein, whena code symbol is presented within the collimated scanning volume: (i)the code symbol is scanned omnidirectionally by the collimated scanningpattern, (ii) at least a portion of the optical energy reflected fromsaid scanned code symbol is directed through said optically admissivewindow, reflected off at least one of the stationary opticallyreflective surfaces, and then reflected off at least one of the rotatingoptically reflective surfaces of the beam sweeping mechanism, and (iii)thereafter the reflected optical energy is collected by the opticalcollection element, and received by the optical receiver for detection,whereupon the electrical signal is produced for processing by the signalprocessor; and wherein the housing is adapted to permit a user tocontrol the direction of said projection axis so as to align thecollimated scanning volume with the bar code symbol on the object to bescanned.